WELDING 


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Metallurgical  and  Chemical  Engineering 


WELDING 

THEORY,  PRACTICE, 
APPARATUS  AND  TESTS 

ELECTRIC,    THERMIT 
AND    HOT-FLAME   PROCESSES 


BY 

RICHARD  N.  HART,  B.  S, 


McGRAW-HILL   BOOK  COMPANY 

239  WEST  39TH  STREET,  NEW  YORK 

6  BOUVERIE  STREET,  LONDON,  E.  C. 

1910 


COPYRIGHT,  1910 

BY  THE 
MCGRAW-HILL  BOOK  COMPANY 


Printed  and  Electrotyped  by 

The  Maple  Press 

Sork,  Pa 


PREFACE 


IN  spite  of  the  numerous  data  on  the  theory,  practice,  appara- 
tus, and  tests  of  welding  contained  in  the  trade  journals  and 
metallurgical  books,  no  previous  attempt  has  been  made  to  present 
this  data  in  sequence  under  one  cover.  But  in  the  last  fifteen 
years  the  subject  has  begun  to  be  of  interest  and  importance.  The 
electric,  thermit,  and  hot-flame  processes  are  welding  all  of  the 
metals  and  are  doing  repeat  and  repair  work  that  has  never  before 
been  attempted.  New  brazing  methods  have  also  been  success- 
fully tried  out  and  the  range  of  good  solders  greatly  increased. 

I  have  given  separate  chapters  to  the  commercial  metals. 
Few  of  the  metallurgies  give  much  space  to  the  working  proper- 
ties of  the  metals,  especially  the  welding  property,  which  is  often 
merely  mentioned. 

Test  and  cost  data  must  be  taken  with  a  grain  of  salt.  The 
test  data  have  been  compiled  from  various  sources.  Those  tests 
given  for  iron  are  standard  and  cannot  be  questioned.  Those 
tests  given  for  the  special  processes  are  more  recent  and  in  most 
cases  have  been  made  by  interested  parties.  They  are  no  doubt 
accurate,  but  at  present  the  special  processes  cannot  be  so  well 
represented  by  test  data,  as  by  the  actual  work  they  turn  out. 
The  same  may  be  said  of  cost  data.  The  prospective  purchaser 
of  welding  machinery  must  figure  the  cost  of  his  apparatus  plus 
the  cost  of  labor  and  the  depreciation.  But  above  all,  he  must 
satisfy  himself  that  the  apparatus  he  chooses  is  the  best  for  his 
kind  of  welding. 

I  wish  to  express  my  thanks  for  assistance  received  from  the 
different  welding  companies  mentioned  herein;  also  to  James 
H.  DeLong,  for  special  analyses;  Dr.  Edward  Hart,  Dr.  Joseph 
W.  Richards,  Prof.  Oliver  P.  Watts,  Otis  Allen  Kenyon,  E.  A. 
Colby,  of  Baker  &  Co.,  and  to  many  others. 

R.  N.  HART. 

Los  ANGELES,  CAL.,  October,  1910. 

V 

222496 


CONTENTS 


PAGE 

Preface .    .    ,  v 

Definitions  and  introduction xi 

Theories  of  welding xiv 

THE  METALS 

Iron .    t i 

Malleable  'ron i 

How  to  weld  iron - .    .  2 

Points  in  practice 3 

Welding  fires 4 

Causes  of  poor  welds 6 

Effect  of  impurities 8 

Tests  of  smith  welds .    .    .  12 

Conclusions 15 

Platinum — Descriptive  and  historical — Welding,  including  irid- 

ium  and  osmium 15 

Gold — Descriptive — Welding  and  soldering 18 

Silver — Descriptive — Welding  and  soldering 19 

Aluminium  —  Descriptive  —  Solders  —  Welding  processes  —  Con- 
clusion   20 

Copper — Descriptive — Welding 25 

Nickel — Descriptive — Welding 27 

Welded  products 28 

Wrought-iron  pipe 29 

Chain  making 29 

Miscellaneous 30 

ELECTRIC  WELDING 

General 33 

The  La  Grange-Hoho  process 34 

The  Zerener  electric  blowpipe 34 

vii 


Vlii  CONTENTS 

PAGE 

The  Bernardos  arc-welding  process 35 

Apparatus  and  current:  Generator — Table,  switches,  controll- 
ing apparatus,  carbon — Workman's  protective  apparatus  38 

Practice 40 

Cutting  metals  with  electric  arc      41 

The  Thomson  process      42 

Apparatus  and  current:  .Generator — Transformer — Regulat- 
ing apparatus — Clamps 43 

Practice 54 

Adaptability — Locomotive  flue-welder 59 

Rail  welding 66 

Electric  resistance  heater 69 

Tests 70 

HOT-FLAME  WELDING 

The  Oxy-acetylene  process 73 

General 73 

Apparatus  and  gases:  The  torch — Electrolysis  of  water — 
Storage  oxygen — Oxygenite — Oxygen  from  chlorate — Acet- 
ylene— The  acetylene  generator — Dissolved  acetylene  .  .  75 

Practice— The   flame 96 

How  to  weld 97 

Adaptability v 101 

Typical  welds  and  repairs:  Repairing  cracks,  steamer  "Eugene 
Periere"  of  the  French  Line — Repairing  corroded  plates 

plates  on  the  "Cholon." 102 

Acetylene  welding  versus  riveting 106 

Repairing  defective  castings 108 

How  to  cut  metals 109 

Costs 112 

Chemistry  and  thermics 113 

Testing 115 

The  Oxy-hydrogen  process 115 

General 115 

Apparatus — The  flame 116 

THERMIT 

The  Thermit  process 121 

General — History 121 

Apparatus  and  rail  welding — Crucible — Mold 123 


CONTENTS  IX 

PAGE 


Practice — Setting  the  pieces — Cleaning  the  pieces — Preheat- 
ing— Safe-guarding  the   mold — Amount  of   thermit — The 
reaction — After  pouring — Nickel  addition — Titanium  addi- 
tion     .    .    .    . 131 

Butt- welding  of  pipes 137 

Mending  defective  castings 141 

Thermit  in  foundry  practice — Poling — Adaptability  ....  142 
Typical  welds— Repair  of  the  " Betsy  Ann" — Repair  of  the 

steamship  "Corunna" — Weld  on  electric  motor  shaft   .  146 

Chemistry  and  thermics— Heat  of  reaction 152 

Testing — Tests  Nos.  1-6 155 

The  Lafitte  welding  plate    . .  158 

The  Ferrofix  brazing  process 160 

Brazing  and  soldering , 165 

Glossary  of  terms .    .    .    .    .    .    . 175 


DEFINITIONS  AND  INTRODUCTION 


According  to  the  Standard  Dictionary,  to  weld  is  to  "  unite, 
as  heated  metal,  in  one  piece  or  mass  under  the  hammer  or  by 
pressure." 

The  Century  Dictionary  says,  "To  unite  or  consolidate,  as 
pieces  of  metal  or  metallic  powder,  by  hammering  or  compres- 
sion, with  or  without  previous  softening  by  heat."  *  *  *  "term 
is  more  generally  used  when  the  junction  of  the  pieces  is  effected 
without  the  actual  fusing  point  of  the  metal  having  been  reached." 
While  the  Standard  adds,  "Metals  are  weldable  in  proportion  to 
the  length  of  time  they  will  stay  under  heat  in  a  plastic  condition 
without  melting." 

Welding  is  distinguished  from  soldering,  which  is,  according  to 
the  Standard,  "To  unite,  as  two  metallic  substances,  by  solder." 
The  Century,  "To  unite  by  a  metallic  cement."  *  *  *  "Every 
kind  must  be  used  as  its  own  melting  point,  which  must  be  al- 
ways lower  than  that  of  the  metals  to  be  united." 

I  give  these  definitions  because  there  is  some  confusion  of  the 
terms;  and  naturally  so,  as  the  two  processes  often  are  undistin- 
guishable.  Thus  two  unlike  metals,  as  iron  and  platinum,  may  be 
welded;  while  a  fractured  steel  bar  may  be  united  by  placing 
platinum  foil  between  the  pieces,  pressing  strongly  together  and 
heating  moderately.  This  is  strictly  welding,  yet  the  platinum 
foil  is  solder.  In  the  recent  processes  of  welding  by  fusion,  the 
molten  metal  becomes  a  solder.  Brazing  is  classed  as  soldering, 
but  when  brass  is  brazed  the  process  is  as  nearly  welding  as  the 
so-called  autogenous  weld. 

The  word  autogenous  is  misapplied  to  welding.  It  means 
self -produced.  The  melted  weld  of  the  oxy-hydrogen  or  acetylene 
flame  is  a  soldering  process  in  which  the  metal  produces  its  own 
solder.  However,  it  makes  a  catchy  trade-name. 

Welding,  under  different  names,  is  a  property  possessed  by 
many  substances,  both  elemental  and  compound.  According  to 

xi 


XI 1  WELDING 

Roberts- Austen,1  who  devotes  considerable  space  to  the  flowing 
property  of  metals,  "welding  is  the  property  possessed  by  metals, 
which  on  cooling  from  the  molten  state  pass  through  a  plastic 
stage  before  becoming  perfectly  solid,  of  being  joined  together  by 
the  cohesion  of  the  molecules  that  is  induced  by  the  application  of 
an  extraneous  force,  such  as  hammering." 

In  general,  welding  occurs  if  cohesion  between  the  molecules  of 
the  two  pieces  can  be  induced.  This  cohesion  may  amount  to 
diffusion  when  the  two  pieces  are  of  unlike  substance,  and  the 
metal  at  the  weld  will  be  found  to  be  an  alloy  of  the  two,  Thus 
gold  and  lead,  pressed  together  for  several  weeks,  will  weld  at 
ordinary  temperature.  At  100  deg.  C.  they  will  weld  in  less 
time,  and  the  weld  will  be  an  alloy  of  gold  and  lead. 

Welding  and  diffusion  are  not  inseparable,  however.  For  the 
welding  by  diffusion  of  lead  and  gold  is  weaker  than  the  first- 
named  cold  weld.  While  the  diffusion  of  mercury  through  an- 
other metal  invariably  produces  weakness  of  that  metal,  some- 
times disintegration. 

Regelation  is  the  name  given  to  the  welding  of  two  pieces  of 
ice.  Faraday  is  credited  with  this  discovery.  He  found  that 
two  pieces  of  ice  slightly  below  freezing  point,  if  pressed  together 
will  weld.  Wrightson2  states  that  both  iron  and  ice  suffer  a 
drop  in  temperature  when  pressed  together.  He  heated  two 
irons  to  the  plastic  state  in  an  electric  welder  and  pressed  them 
together.  The  recording  pyrometer  showed  a  sudden  fall  of 
from  19  deg.  to  57  deg.  C.  He  further  states  that  iron  in- 
creased almost  7  per  cent,  in  volume  on  becoming  plastic,  and 
tries  to  trace  an  analogy  between  the  behavior  of  iron  and  ice. 
It  has  since  been  found  that  revelation  is  a  property  possessed 
in  some  degree  by  most  crystalline  substances.  Pure  crystalline 
salts  will  regelate  under  pressure  at  moderate  temperature.  Even 
such  a  substance  as  bismuth  will  regelate. 

Evidently  welding  depends  upon  two  things : 

i.   The  flow. 

Most  of  the  so-called  solids  are  fluid  to  some  extent.  Highly 
crystalline,  refractory  rocks  will  flow  under  great  pressure.  The 

1  "Introduction  to  Metallurgy,"  p.  47. 

2  Journal  of  the  Iron  and  Steel  Institute,  1895,  Vol.  I,  p.  499. 


DEFINITIONS    AND    INTRODUCTION  Xlll 

walls  of  some  deep  mines  have  flowed  together  in  the  course  of 
time.  A  rod  of  glass  or  of  sealing-wax  will  bend  or  flow  if  it 
supports  a  weight  for  several  days.  Lead,  sodium,  etc.,  flow 
readily  under  pressure. 

Flow  is  almost  synonymous  with  malleability,  the  difference 
being  a  matter  of  time.  Many  substances  which  flow  slowly  will 
not  withstand  the  shock  of  the  hammer. 

Most  metals  flow  at  all  temperatures  from  normal  to  melting 
point,,  but  they  are  the  most  easily  weldable  within  the  range  of 
greatest  plasticity.  But  their  welding  also  depends  upon— 

2.  The  wetting  or  cohesion  of  the  two  substances. 

Two  pieces  of  the  same  or  different  substance  will  not  weld  if 
their  surfaces  do  not  cohere,  no  matter  how  malleable  or  fluid 
they  may  be.  Aluminum  is  a  notable  instance.  The  metal  is 
quite  malleable  at  most  temperatures,  but  a  microscopic  film  of 
oxid  prevents  the  two  surfaces  from  wetting  one  another.  Iron  in 
a  lesser  degree  is  troubled  with  a  coating  of  oxid  at  welding  tem- 
perature. Any  flux  which  will  clean  off  both  surfaces  will  allow 
a  weld  to  be  made.  In  proportion  to  the  ease  with  which  one  can 
have  and  hold  a  clean  surface  of  the  metals  in  the  range  of  plas- 
ticity, in  that  proportion  will  welding  be  feasible.  The  welding 
of  malleable  metals  is  dependent  on  the  behavior  of  the  oxids 
which  form  on  their  surface.  In  proof  of  this  is  the  remarkable 
experiment  of  Chernoff 1  in  1877.  He  showed  that  a  partial  weld 
of  two  pieces  of  iron  could  be  made  at  the  low  temperature  of  650 
deg.  C.,  which  is  at  least  700  deg.  below  common  welding  heat. 
The  two  surfaces  were  planed  and  highly  polished.  Pressure  was 
applied  for  several  days,  when  it  was  found  that  there  was  a 
partial  weld.  This  is  similar  to  the  well-known  experiment  in 
physics  where  two  plane  and  highly  polished  surfaces  of  glass 
are  pressed  together.  The  surfaces  will  cohere  to  some  extent. 

These  two  experiments  seem  to  show  that  whatever  assists 
cohesion,  assists  the  welding.  There  are  numerous  instances  of 
welding  among  non-metallic  substances  which  do  not  oxidize 
at  the  welding  heat.  Glass  is  too  well-known  to  need  explana- 
tion. Pieces  of  horn  can  be  joined  under  pressure  of  hot  plates 
if  the  horn  be  kept  moist. 

1  Revue  Universalle  des  Mines,  Vol.  I,  1877,  p.  411. 


XIV  WELDING 

Metals  newly  nascent,  in  a  fine  powder,  can  be  welded  into  a 
solid  piece  by  a  stroke  of  the  hammer.  Apparently  for  the  reason 
that  the  grains  of  powder  have  bright,  clean  faces.  Most  of  the 
malleable  metals  are  so  weldable. 

THEORIES  OF  WELDING 

In  1877,  Holley1  advanced  the  theory  that  irons  weld  in  pro- 
portion to  their  mobility  or  flowing,  and  inversely  as  oxidation 
of  the  welding  surfaces  occurs.  He  thought  that  the  more 
plastic  or  more  nearly  melting  point  the  irons  were,  the  more 
readily  they  would  weld.  But  with  every  increase  in  heat  was  a 
corresponding  readiness  to  oxidize — especially  on  the  part  of 
carbon  and  iron.  This  oxid  interposed  a  mechanical  difficulty 
to  perfect  welding. 

This  theory  does  not  satisfy  Campbell2  who  insists  that  im- 
purities tend  to  crystallization  in  the  body  of  the  iron.  Carbon, 
which  is  the  principal  offender,  and  sulphur,  phosphorus,  and 
other  ingredients,  all  form  alloys  or  compounds  with  the  pure  fer- 
rite.  Ferrite  itself  is  exceedingly  malleable  and  mobile.  But  a 
mixture  of  ferrite  and  several  of  the  carbon  compounds,  as  cemen- 
tite,  martensite,  etc.,  is  stiff  above  red  heat  in  proportion  to  the  car- 
bon present.  Campbell  thinks  that  such  a  steel,  which  is  really  a 
mineral  with  a  granitic  structure,  will  not  weld,  because  it  refuses 
to  flow.  He  claims  that  oxidation  troubles  are  actually  less, 
because  the  chemical  combination  of  the  iron  oxid  with  the 
impurities  and  their  oxids  would  give  a  self-fluxing  surface. 

According  to  Campbell,  then,  those  impurities  which  caused 
decided  crystallization  with  accompanying  brittleness,  interfered 
with  the  flow  at  high  heat  and  prevented  welding.  Manganese, 
it  is  true,  makes  a  more  brittle  iron,  up  to  i .  20  per  cent;  but 
it  prevents  crystallization  of  sulphur,  etc.,  and  is  an  aid  in  welding. 

For  ordinary  and  commercial  purposes  the  welding  must  be 
done  in  a  few  seconds'  time,  and  the  previous  cleaning  and  heating 
must  not  take  long.  This  at  once  limits  to  a  very  few  the  num- 
ber of  metals  which  can  be  welded;  were  it  not  for  the  recent 

1  Trans.  American  Institute  of  Mining  Engineers,  Vol.  VI,  p.  112. 

2  "Metallurgy  of  Iron  and  Steel,"  p.  589. 


THEORIES    OF    WELDING  XV 

remarkable  advance  due  to  the  electric,  oxy-hydrogen  and  acety- 
lene processes  of  melting,  welding  would  be  confined  to  iron,  plat- 
inum, nickel,  and  gold.  Other  metals  would  be  joined  by  solder- 
ing and  brazing,  and  even  then  the  metal  worker  would  have  great 
difficulties  with  aluminum  and  many  alloys. 

I  will  first  take  up  iron  and  steel  welding.  As  much  research 
work  has  been  done  on  the  metallurgy  of  iron  as  on  all  of  the  other 
metals  combined.  It  is  extremely  probable  that  many  of  the 
difficulties  and  problems  arising  from  proportions  of  impurities 
and  methods  of  producing  will  apply  equally  to  other  metals. 
For  this  reason,  and  because  of  its  overwhelming  importance,  I 
will  treat  of  iron  more  thoroughly. 


WELDING 


PART  I— THE  METALS 

IRON 

Pure  or  nearly  pure  iron  is  readily  weldable  at  a  white  heat. 
Malleable,  or  nearly  pure  wrought  iron,  is  known  as  weld  iron. 
The  range  of  temperature  in  which  it  can  be  welded  is  very 
wide:  it  runs  from  the  imperfect  weld  at  cherry- red,  to  dazzling 
white,  when  the  welding  property  is  lost  just  before  the  iron 
melts.  According  to  Pouillet,  the  different  colors  of  heated 
metals  are  represented  approximately  by  the  temperatures  given: 

Deg.  C 

Incipient  red 525 

Dark  red 700 

Incipient  cherry 800 

Clear  cherry-red 1000 

White 1300 

Dazzling  white 1500 

Melting 1550 

Wrightson1  states  that  he  found  iron  to  increase  in  volume  as 
much  as  7  per  cent,  when  passing  into  the  plastic  stage. 

Malleable  Iron. — Weld  iron  is  a  name  occasionally  used  to 
describe  malleable  iron,  indicating  that  it  is  pure  enough  to  be 
welded.  Malleable  iron  is  produced  by  the  puddling  process. 
It  is  made  by  melting  up  pig  iron  and  scrap  in  an  open-hearth 
furnace  and  burning  out  the  greater  part  of  the  silicon,  man- 
ganese, and  carbon  in  the  order  named.  As  the  burning  continues 
the  melting  point  of  the  iron  rises,  and  it  becomes  a  pasty  mass 
permeated  with  slag  from  the  stirring.  This  nearly  pure  iron 
is  gathered  into  "puddle  balls,"  and  taken  to  the  rolls  at  a  white 
heat.  It  is  rolled  or  hammered  out  into  long  strips,  the  strips 
are  cut,  reheated  to  white  heat,  and  welded  together  between  the 
rolls  or  beneath  the  hammer.  To  produce  the  finest  wrought 

1  Journal  of  the  Iron  and  Steel  Institute,  1895,  Vol.  I,  p.  463. 

I 


2  WELDING 

iron,  the  process  of  rolling  and  welding  is  repeated.  This  is 
the  puddling  process  in  brief;  its  object  is  to  squeeze  and  work 
the  slag  out  of  the  iron  and  to  give  the  iron  a  fibrous  structure 
like  rolled  copper. 

The  principal  chemical  difference  between  wrought  iron  and 
.steel  is  the  carbon  content.  In  fact,  except  for  its  high  carbon, 
basic  open-hearth  steel  is  purer  than  most  malleable  irons. 

All  weldable  iron  is  not  malleable,  but  it  is  weldable  in  pro- 
portion  to   its   malleability. 

\^"~  ^    F^  — - —       -A    As  is  seen  in  the  foregoing 
^~~~^  1  \    process,  the  iron  is  welded 

several  times. 

FIG.  i. — Views  of  scarfed  bars  for  TT  ±      -nr   ij    T 

lap  welding.  How    to    Weld    1™!!.— - 

The     mechanics     of     a 

"smithed"  weld  is  in  the  main  as  follows:  Suppose  the  smith 
wishes  to  join  two  short  bars  of  malleable  iron,  of  cross-section 
i  by  2  inches.  He  first  hammers  or  cuts  a  convex  bevel  or 
"scarf"  on  the  ends  of  each  bar,  as  shown  in  Fig.  i. 

The  heating  must  be  done  in  a  coke  or  coal  forge.  Coke  is 
the  best  fuel  for  the  reason  that  it  gives  a  good  reducing  flame. 
The  fire  is  blown  with  the  bellows  until  it  is  at  a  high  heat.  The 
ends  of  the  bars  are  thrust  well  into  the  midst  of  the  ignited 
coke  and  more  coke  is  piled  over  them.  The  blowing  is  con- 
tinued until  the  bars  are  red-hot  on  the  ends,  when  the  smith 
takes  them  out  with  pliers  and  dips  them  into  pure  sand  or  borax 
near  by.  This  is  the  flux,  and 
it  so  acts  on  the  surface  of  the 
iron  as  to  clean  it  of  rust  and 

forms   a   glass    that   protects    _, 

.  F  FIG.  2. — Bars  in  position  for  lap  welding. 

the  fresh  iron    from   further 

rust.  The  smith  puts  his  irons  back  into  the  forge  again  and 
heats  them  until  white. 

When  white,  or  nearly  white-hot,  the  smith  takes  one  bar  in 
his  pliers,  his  helper  takes  the  other,  and  they  place  them  together 
on  the  anvil,  the  one  lapping  the  other  (Fig.  2).  Both  the  smith 
and  his  helper  give  the  pieces  quick,  light  blows  with  their 
hammers  until  the  plastic  iron  is  well-joined.  They  turn  the 
irons  while  hammering  to  get  an  even  weld  on  all  sides. 


IRON  3 

The  smith  will  try  to  weld  at  a  white,  but  not  a  dazzling  white, 
heat,  and  he  will  try  to  complete  it  without  putting  it  back  into 
the  fire  for  a  reheating. 

When  the  weld  is  finished,  he  may  give  it  a  special  shape  by 
placing  it  between  swage  blocks  and  hammering. 

This  simple  operation  of  welding  requires  much  skill,  as  will 
appear.  The  smith  may  find  that  with  all  his  skill  his  joint  is 
bad  or  that  his  iron  will  not  join  at  all. 

Points  in  Practice. — In  practice  there  are  the  usual  number 
of  details  requiring  skill  that  the  smith  must  observe. 

The  contact  faces  should  always  be  shaped  so  that  their 
middle  points  touch  first  and  so  that  hammering  causes  union 
first  at  the  middle.  This  prevents  slag  becoming  enclosed. 

The  heating  should  be  done  rather  slowly,  so  that  the  pieces 
will  be  of  uniform  heat  at  the  weld.  Both  irons  should  be  of  the 
same  temperature.  To  effect  this  the  smith  must  not  blow  up 
his  fire  too  hot  and  must  watch  the  color  of  both  irons.  A  deep 
bed  of  coals  will  give  a  flame  the  least  oxidizing,  because  most  of 
the  oxygen  will  burn  to  carbon  monoxid  or  dioxid. 

The  welding  heat  is  quite  different  for  different  irons.  The 
smith  must  use  his  judgment,  taking  good  care  he  does  not  over- 
heat his  irons.  Overheated  iron,  miscalled  "burnt  iron,"  will 
be  brittle  on  cooling.  Steel  is  much  more  sensitive  to  overheat- 
ing than  iron.  It  is  seldom  safe  to  heat  steel  above  redness. 

The  iron  should  be  well  fluxed  directly  on  the  contact  surfaces, 
and  not  merely  around  them,  as  is  too  often  the  case.  The  com- 
mon fluxes  for  iron  are  pure  silica  (river  sand)  and  borax.  Im- 
pure malleable  irons  are  self -fluxing  to  a  certain  degree,  but  this 
cannot  be  relied  on.  Other  fluxes  are  calcined  borax  and  sal 
ammoniac.  One  writer1  recommends  powdered  marble,  which 
is  limestone,  the  flux  of  the  blast  furnace.  Borax  is  recommended 
for  steel  on  steel  or  steel  on  iron,  as  silica  is  inadequate.2  Besides 
fluxing  the  bars  before  raising  them  to  welding  heat,  the  smith 
may  sprinkle  calcined  borax  on  the  irons  when  they  are  ready  to 
weld,  to  replace  it  on  surfaces  accidentally  rubbed  bare  in  the 
forge. 

^'The  Blacksmith's  Guide,"  J.  S.  Sallows. 

2  "Testing  of  Materials  of  Construction,"  W.  C.  Unwin,  1899,  p.  292. 


4  WELDING 

The  hammering,  or  "working,"  is  very  important,  and  must 
be  done  rapidly.  The  smith  manipulates  his  bars  so  that  welding 
begins  at  a  middle  point  and  works  outward,  driving  the  slag 
away  from  it.  The  first  few  blows  of  the  hammer  should  not  be 
heavy.  If  the  pieces  are  large  or  the  smith  slow,  his  heat  will 
fall  before  the  weld  is  finished  and  he  must  put  his  bars  back  in  the 
fire.  Second  heating  must  be  avoided  if  possible;  slag  is  apt  to 


FIG.  3. — Lap  weld.     No  upset.  FIG.  4.— Lap  weld.     Upset. 

get  in  the  weld  or  the  pieces  may  become  "burnt,"  to  say  nothing 
of  the  time  lost. 

The  different  kinds  of  welds  known  to  the  smith — butt,  lap, 
scarf,  jump,  cleft — are  variations  of  simple  welds.  Illustrations 
of  them  and  of  how  the- stock  should  be  shaped  are  given  in  fig- 
ures 3  to  7.  The  method  of  hammering  will  suggest  itself  in 
each  case.  Jump  and  butt  welds  will  have  sufficient  upset  to 
work  on,  while  scarf  welds  will  not  unless  the  pieces  are  jumped 
or  over-lapped  considerably. 

Welding  Fires,  etc. — The  ordinary  fire  used  by  the  smith  for 


(I 


FIG.  5. — Jump  weld.  FIG.  6. — Butt  weld. 

his  welding  is  a  deep  bed  of  coke.     But  the  fire  may  be  fed  with 
hard  or  soft  coal;  it  may  also  be  a  gas  or  oil  flame. 

For  blacksmithing,  the  coke  fire  is  much  the  best.  In  this 
fire  nearly  pure  carbon  is  burned,  and  the  resultant  gases  are 
carbon  monoxid  and  dioxid.  The  carbon  monoxid  and  the  coke 
are  reducing  in  their  action.  They  will  prevent  the  metal  heated 
from  oxidizing  and  will  even  clean  the  metal  of  scale. 


IRON  5 

Hard  coal  can  be  used,  but  in  a  small  forge  it  is  impossible  to 
get  a  hot  enough  fire.  Soft  coal  is  a  poor  coal  for  forge  work.  It 
has,  as  a  rule,  high  sulphur,  which  the  hot  iron  readily  absorbs  to 
its  detriment.  While  the  thick  carbon  smoke  of  the  flame  is  apt 
to  collect  on  the  iron  in  an  oily  soot  unless  the  flame  can  be  kept 
hot  enough. 

Gas  and  oil  flames  are  often  used  for  chain  welding  and  similar 
operations.  The  gas  or  oil  should  be  fairly  free  from  sulphur. 

The  gas  flame  is  made  by  in-      

jecting  the  gas  through  a  large     vl 

Bunsen  burner.     Air  is  intro- 

FIG.  7  —  Cleft  weld. 

duced   through   holes  in   the 

burner  a  short  distance  from  the  burner  end.  Or  if  the  gas  is 
under  sufficient  pressure  to  make  a  roaring  flame,  it  will  take  in 
enough  air  at  the  end  of  the  burner.  The  proper  mixture  gives 
a  nearly  colorless  flame.  The  quickest  and  best  way  to  tell  if  a 
flame  is  right  for  welding  is  to  heat  in  it  a  small  piece  of  steel  or 
soft  iron.  If  the  flame  has  too  much  air,  the  metal  piece  will 
rust  and  scale  off  in  the  flame.  If  too  little  air,  the  soot  will 
collect  on  the  metal  and  it  will  not  heat  quickly.  Gas  flame  is 
the  most  convenient  for  most  purposes.  It  is  easy  to  regulate 
and  can  be  turned  on  the  iron  while  welding.  In  this  way  iron 
can  be  welded  without  flux.  When  chain  is  made  the  links  are 
hung  on  a  bar  above  a  long  narrow  furnace  of  fire  bricks.  The 
flame  is  played  beneath. 

The  oil  flame  is  a  cheaper  flame  than  gas.  It  can  be  manipu- 
lated in  the  same  way  as  a  gas  flame.  But  the  oil  must  be  free 
from  sulphur  compounds  to  make  a  safe  flame. 

It  has  lately  been  tried  to  burn  gases  that  have  been  preheated. 
If  coal  gas,  starting  to  burn  at  35  deg.  C.,  will  give  a  combustion 
point  of  about  2000  deg.,  then  by  preheating  it  to  about  800 
deg.  C.  and  burning,  there  will  be  a  gain  of  400  or  500  deg. 
in  the  temperature  of  the  flame.  In  other  words,  the  welder 
has  boosted  his  flame  up  to  about  2500  deg.,  a  very  respect- 
able temperature. 

The  preheating  is  done  by  passing  the  gases  through  copper 
coils  which  are  nested  above  the  welding-flame  flue,  and  which 
receive  the  heat  from  the  welding  flue. 


O  WELDING 

Causes  of  Poor  Welds. — Suppose  we  have  an  iron  or  steel 
that  will  weld.  There  are  still  many  good  reasons  for  discrediting 
the  safety  of  the  joint  until  it  has  been  tested.  They  are : 

i.  Imperfect  Contact. 

a.  The  two  surfaces  may  give  the  appearance  of  perfect 
union,  but    a   considerable  percentage  of   the   central  portion 
may  be  faulty.     For  if  the  metal  in  course  of  puddling  is  not 
relieved  of  its  enclosed  slag,  this  will  be  finally  pressed  out  into 
thin  laminae.     These  cleaving  planes  will  be  parallel  with  the 
bar  until  it  is  welded,  when  they  will  be  upset  in  all  directions  at 
the  joint.     A  network  of  such  planes  now  running  across  the 
bar  instead  of   parallel  to  it  will  greatly  diminish  the   tensile 
strength. 

b.  Then,  again,  the  smith  may  carelessly  allow  some  of  his 
flux  to  stay  within  the  weld.     All  the  hammering  in  the  world 


FIG.  8.— Correct  shapes  for  jump  FIG.  9.— Incorrect  shapes  for  jump 

and  lap  welds.  and  lap  welds. 


will  not  remedy  it.  In  most  cases  one  of  the  pieces  can  be 
scarfed  or  pointed,  so  that  the  first  contact  of  the  hot  pieces  will 
be  at  a  central  point.  As  the  hammering  proceeds,  the  slag 
will  be  forced  out  of  the  joint  as  fast  as  the  pieces  weld  (see 
Fig.  2).  This  caution  applies  equally  to  the  smithed  weld  or 
the  Lafitte  joint  (see  page  158). 

c.  Or  the  smith  may  not  flux  his  bars  correctly,  thereby 
allowing  unreduced  and  uncombined  oxid  of  iron  to  get  in  the 
weld.  It  is  not  a  difficult  thing  to  get  this  rust  incorporated  in 
the  weld,  because  it  is  soluble  in  iron.  Dissolved  rust  makes  a 
" burnt"  or  brittle  joint.  Clean  silica  sand  is  the  common  flux. 
The  smith  dips  his  hot  bars  into  a  box  of  the  sand  kept  near  by, 
and  often  sprinkles  a  handful  over  the  pieces  when  hammering 
if  the  pieces  are  large.  The  reaction  between  the  sand  and  the 
rust  is  rapid.  Iron  silicates,  easily  fusible,  are  formed.  They 


IRON  7 

cover  the  fresh  iron  surface  with  a  thin  glass,  which  prevents 
further  oxidation. 

2.  Insufficient  hammering  or  "working"  may  account  for  the 
poor  weld.     The  iron  may  be  perfectly  joined,  yet  the  structure 
is  weak  and  uncertain.     Wrought  iron  has  a  fibrous  structure 
similar  to  wood.     The  smith  must  do  his  best  to  continue  this 
structure  through  the  weld.     With  a  lap  weld  he  can  start  with  a 
heavy  upset  which  can  be  hammered  down.     Hammering  serves 
the  double  purpose  of  consolidating  the  metal  and  of  laying 
the  cleavage  planes  perpendicular  to  the  blows.     Much  ham- 
mering is  impossible  with  jump  and  butt  welds.     The  lapweld- 
ing  of  wrought-iron  pipe  and  the  scarf-welding  of  chain  links- 
must  depend  on  pressure  for  their  perfect  finishing.     Welds  of 
steel  cannot  often  be  much  benefited  by  working.     Steel  is  an 
alloy,  without  structure.     To  be  strong  it  must  be  solid  and 
homogeneous.     Campbell's  advice  is  to  keep  the  critical  tem- 
perature high  and  keep  down  the  silicon  and  phosphorus  when 
choosing  your  steel. 

3.  Too  high  a  heat  is  responsible  for  some  bad  welds.     Very 
great  heat  will  unsettle  the  structure  of  the  iron  in  the  stock  a 
considerable  distance  from  the  joint.     Because  the  bar  breaks 
near,  but  not  on,  the  joint,  is  no  proof  of  the  soundness  of  the 
weld.     The  structure  of  the  iron  is  impaired  wherever  the  heat  is 
beyond   the  critical  point  of   crystallization  of   any  important 
impurity.     By  this  is  meant  that  if  there  be  an  appreciable 
amount  of  carbon,  for  example,  it  will  tend  to  mineralize  the  iron 
when  the  latter  is  cooled  down  past  the  crystallization  point  of  the 
first  carbon-iron  mineral.     A  number  of  other  impurities,  silicon, 
aluminum,  arsenic,  etc.,  are   presumed   to  act  in  like  manner. 
So  the  smith  must  work  his  weld  and  also  all  of  the  surrounding 
metal   that   has   been   raised   above   this   critical   temperature. 
Just  what  is  the  critical  temperature  is  unknown  to  him,  because 
it  varies  with  every  iron,  according  to  the  amount  and  proportion 
of  its  impurities, 

Oftentimes  welds  are  made  which  cannot  be  worked  to 
advantage.  Such  welds  are  apt  to  be  weak.  The  only  present 
remedy  is  to  select  for  such  purpose  iron  as  free  as  possible  from 
objectionable  impurities.  Machine  welds,  such  as  small  chain 


8  WELDING 

links  and  small-bore  pipe,  where  the  entire  piece  must  be  heated, 
are  especially  subject  to  this  disadvantage. 

4.  Large  welds  are  unsafe. 

Just  what  is  the  maximum  cross-section  of  practicable  welding 
cannot  be  safely  laid  down.  Welding  is  not  advisable  where  it  is 
difficult  to  get  a  good  welding  heat,  to  flux  properly,  to  joint  the 
pieces  well  and  accurately,  or  to  work  the  weld  when  made.  To 
weld  a  ship's  sternpost  or  skeg  or  rudder-post  was  a  matter  of 
weeks  of  expensive  and  often  hopeless  labor  before  the  advent 
of  thermit  (see  page  147).  To  weld  a  large  driving- rod,  an 
embossing  die,  crushing  roll,  or  propellor  shaft  was  impossible. 
The  largest  iron  pipe  used,  however,  could  be  welded;  also 
chain  links  a  foot  or  more  long,  and  2-  or  3-inch  stock  could 
be  safely  welded. 

Campbell  says,1  "Welds  of  large  rods  of  forging  steel  are 
entirely  unreliable.  Electric  methods  do  not  offer  a  solution  of 
the  problem,  for  during  the  process  the  metal  is  heated  far  be- 
yond the  critical  temperature."  Thermit,  since  discovered,  does 
offer  a  partial  solution,  because  a  thermit  weld  can  be  reinforced 
with  as  much  metal  as  needed,  and  the  metal  itself  can  be  varied 
to  meet  the  requirements.  Its  cost  is  to  be  considered.  The 
oxy-acetylene  melt-weld  should  recommend  itself  for  like  reasons. 
More  than  one  torch  can  be  used  for  large  work  (see  page  75). 

Effect  of  Impurities,  etc. — In  order  to  make  a  good  weld 
of  iron,  the  metal  must  possess  plasticity,  which  is  directly  affected 
by  the  contained  impurities.  The  welding  temperature  seems  to 
be  the  point  at  which  the  iron  becomes  semiplastic,  but  is  still  not 
sufficiently  hot  to  burn  or  oxidize  rapidly.  For  the  reason  that 
this  temperature  varies  considerably  for  the  different  alloys  of 
iron,  it  is  impracticable  to  make  any  definite  rules.  A  number  of 
impurities  or  alloy  formers  affect  the  welding  property  to  a  marked 
degree  even  when  present  in  fractional  parts  of  i  per  cent.  Sub- 
stances which  cause  "red  shortness,"  such  as  sulphur,  or  which 
oxidize  to  form  an  impervious  skin,  such  as  aluminum,  must  be 
avoided  in  iron. 

In  the  case  of  cast  iron,  which  is  iron  high  in  carbon  and  silicon, 
the  metal  passes  suddenly  from  a  crystalline  to  a  liquid  condition. 

1  "Metallurgy  of  Iron  and  Steel  "  p.  588. 


IRON  9 

It  cannot,  therefore,  be  welded  over  the  smith's  forge,  and  can  be 
welded  only  by  one  of  the  recent  special  processes. 

There  are  an  infinite  number  of  kinds  of  iron,  due  to  the  pro- 
portions of  the  combined  impurities  and  the  method  of  treatment 
during  the  nulling.  Each  of  these  so-called  alloys  will  act  dif- 
ferently at  the  welding  temperature,  while  many  of  them  cannot 
be  welded  by  the  smith  at  any  temperature.  There  are  a  few 
general  rules  which  will  help  the  worker  in  the  selection  of  his 
material.  But  there  is  so  much  room  for  failure  in  welding  the 
best  irons  that  what  cannot  be  blamed  on  the  smith  and  his 
material  must  be  laid  to  the  devil. 

Carbon  in  the  combined  state  should  be  kept  below  0.30  per 
cent,  because  it  is  a  hardener  and  makes  brittle  in  the  combined 
state.  Carbon  has  been  found  to  amalgamate  with  iron  to  form 
a  number  of  alloys,  which  are  unworkable  in  proportion  to  their 
carbon  content.  W.  C.  Unwin1  gives  0.90  carbon  as  the  limit 
for  welding  iron  with  silica  flux;  i.io  carbon  as  the  limit  with  any 
flux.  These  alloys,2  pearile,  martensite,  cementite,  etc.,  mineralize 
in  the  iron  and  form  a  granitic  structure  on  cooling.  It  is  likely 
that  all  of  the  mineral  impurities  of  iron  behave  in  this  manner. 

In  the  uncombined  form,  as  graphite,  carbon  does  not  affect 
the  welding  property,  except  that  it  becomes  an  enemy  to  the 
homogeneous  structure  of  the  metal,  just  as  does  slag. 

Slow  cooling,  drawing  the  temper,  keeps  the  combined  carbon 
at  a  minimum.  Silicon  in  a  quantity  approximately  over  i  per 
cent  and  aluminum  even  more  potently,  also  reduce  combined 
carbon  to  graphite.  However,  the  objection  to  silicon  is  that  it 
makes  a  brittle  alloy,  and  aluminum  oxidizes  to  the  disadvan- 
tage of  the  metal.  Slow  cooling  is  valueless  for  the  reason  that 
welding  is  done  at  a  high  heat,  when  iron  is  capable  of  absorbing 
carbon  in  greater  quantity. 

Hence  high  carbon  in  the  stock  cannot  be  toned  down  and 
should  be  avoided.  It  should  never  be  above  0.50,  and  ought 
to  be  below  0.25  for  the  best  results. 

Silicon  causes  brittleness,  which  does  not  yield  to  welding 
heat.  It  must  be  kept  below  0.20  per  cent.  Silicon  is  the 

1  "Testing  of  Materials  of  Construction,"  W.  C.  Unwin. 

2  Wm.  Campbell,  Electrochemical  and  Metallurgical  Industry,  Feb.,  1904. 


10 


WELDING 


element  which  differentiates  cast  iron  from  mild  irons  and  steel. 
An  iron  with  gray-colored  fracture  contains  too  much  silicon  to 
use  in  welding. 

Welding  Property  of  Silicon  Steels1 


The  weld 

Si 

G 

P 

S 

Mn 

Unsatisfactory 

0.21-5.08 

0.14-0.26 

0.08 

0.05 

o.  1  4—0.  29 

Perfect 

0.01-0.504 

0.16-0.18 

0.051-0.121 

0.028-0.094 

0.455-0.622 

It  will  be  noted  that  the  second  series  of  steels  gave  perfect 
welds  with  a  content  of  0.504  silicon,  by  above  analysis;  prob- 
ably accounted  for  by  the  high  manganese,  which  will  prevent 
crystallization. 

Phosphorus  makes  the  " rotten  iron"  for  thin  and  sharp  cast- 
ings when  present  in  quantity  approximately  over  o.  10  per  cent. 
Malleable  iron  for  welds  should  contain  less  than  0.03  per  cent 
of  it,  not  so  much  to  assist  welding,  as  to  insure  a  strong  joint  on 
cooling. 

Sulphur  is  one  of  the  deadly  enemies  of  the  smith.  Its  effect 
on  iron  is  especially  disastrous  at  welding  temperature,  even  when 
not  otherwise  apparent.  In  quantity  approximating  over  o.io, 
it  causes  "  red  shortness,"  brittleness.  It  should  be  kept  as  low  as 
possible.  Manganese  is  the  remedy  for  sulphur,  used  in  the  pro- 
duction of  iron,  but  the  smith  cannot  correct  it  with  manganese 
himself.  Very  low  sulphur  content  is  the  secret  of  the  success  of 
Swedish  iron  in  the  arts. 

Manganese  may  be  present  up  to  about  i .  50  per  cent,  in  iron 
or  steel  to  be  welded.  Up  to  this  limit  its  effect  is  generally 
beneficial.  Campbell  states  that  between  2  and  6  per  cent  it 
forms  a -brittle  unworkable  alloy.  Hadfeld's  steel,  with  about 
7  per  cent,  manganese,  again  becomes  malleable. 

Manganese  is  the  cheapest  tonic  of  the  iron  producer.  It 
reduces  both  sulphur  and  oxygen  in  the  iron  and  rises  to  the  top 
as  slag.  The  remainder,  if  any,  forms  a  tough  workable  alloy 
with  the  iron. 

1  Campbell,  "  Metallurgy  of  Iron  and  Steel." 


IRON  II 

Nickel  steel  welds  readily  at  all  compositions.  Nickel  is  a 
valuable  addition  to  iron,  because  small  percentages  of  it  greatly 
increase  the  tensile  strength  without  impairing  the  elasticity. 
It  is  also  valuable  because  it  prevents  rust  in  its  iron  alloys  to  a 
marked  degree.  Nickel  steels  of  from  2.05  to  4.95  per  cent 
nickel  are  specifically  mentioned  as  weldable  if  the  carbon  is 
kept  down.1 

Chrome  steel2  can  be  welded.  The  first  hammering  must  be 
very  gentle  so  that  the  metal  will  not  fly  to  pieces. 

Aluminum. — There  is  some  uncertainty  about  the  effect  of 
small  quantities  in  iron.  In  amounts  above  3  per  cent  it 
forms  a  valuable  alloy  with  steel,  which  is  highly  fluid  on  melting. 
0.50  per  cent  increases  the  tensile  strength  and  elastic  limits 
from  3000  to  8000  pounds  and  lessens  the  ductility.3  Odel- 
stjerna4  says  that  only  0.002  aluminum  gives  inferior  steel 
castings,  the  fracture  being  coarsely  crystalline. 

A  serious  count  against  aluminum,  if  it  be  true,  is  that  it 
oxidizes  in  its  alloys  and  coats  them  with  a  skin.  This  would 
seriously  affect  the  welding,  because  this  skin  is  a  very  refractory, 
unmanagable  substance.  Reliable  data  are  wanting. 

Copper  is  generally  believed  to  be  harmful  in  malleable  iron. 
However  Campbell5  in  his  welding  experiments  used  bars  con- 
taining 0.35  per  cent,  with  excellent  results.  He  says:  "The 
critical  temperature  at  which  the  steel  ceases  to  be  malleable 
and  weldable  varies  with  every  steel.  It  is  lower  with  each 
associated  increment  of  copper;  it  is  higher  with  each  unit  of 
manganese,  and  it  is  lower  in  steel  that  has  been  cast  too 
hot." 

Arsenic  steel,  with  less  than  0.20  per  cent  arsenic  will  weld 
as  usual.  Between  o.  20  and  i .  20  per  cent  a  flux  of  borax  and 
sal  ammoniac  is  needed.  2.75  per  cent  arsenic  prevents  welding 
altogether,  and  the  iron  behaves  like  pig  iron.6  Campbell7  claims 
that  so  small  an  amount  as  0.093  impairs  the  welding  property. 

llron  Age,  July  25,  1905. 

2  R.  Brown,  Journal  of  the  Iron  and  Steel  Institute,  1896,  Vol.  I,  p.  472. 

3  "Metallurgy  of  Iron  and  Steel,"  Wm.  Campbell,  p.  477. 

4  Transactions  American  Institute  Mining  Engineers,  Vol.  XXIV,  p.  312. 

5  "Metallurgy  of  Iron  and  Steel,"  p.  467. 

6  Iron  Age,  April  13,  1899. 

7  "Metallurgy  of  Iron  and  Steel,"  p.  478. 


12  WELDING 

He  says  that  o .  20  per  cent,  of  arsenic  increases  the  strength  and 
reduces  toughness. 

Nitrogen  content  is  not  a  subject  for  the  smith  to  bother  about. 
Nitrogen  has  been  blamed  recently  for  otherwise  unaccountable 
failures  of  chemically  good  iron.  E.  J.  Sjostedt1  claims  that 
infinitesimal  quantities  of  it  cause  red  and  yellow  shortness.  He 
claims  that  a  furnace  producing  trisilicate  slag  gave  iron  with 
0.003  per  cent  nitrogen;  bisilicate  slag,  0.016  per  cent  nitrogen; 
monosilicate  slag,  .024  per  cent  nitrogen.  0.006  per  cent,  he  says, 
is  the  limit  for  good  steel  and,  presumably,  for  good  welding  steel. 

However,  there  is  at  present  no  easy  way  of  recognizing  its 
presence,  and  it  cannot  be  guarded  against. 

Tests  of  Smith  Welds. — Campbell  made  a  series  of  tests  of 
smithed  welds  of  all  of  the  different  kinds  of  steel  and  of  wrought 
iron,  the  results  of  which  are  given  in  tabulated  form  in  his 
"Metallurgy  of  Iron  and  Steel."  Four  smiths  of  ability  and 
experience  welded  the  metal  in  flats  and  rounds  of  size  and  shape 
most  convenient  for  handling.  And  though  the  men  knew  their 
bars  would  be  tested,  their  welds  were  often  far  from  satisfactory. 
"  Picking  out  the  worst  individual  weld  of  each  workman,  black- 
smith 'A'  obtained  only  70  per  cent,  of  the  value  of  the  original 
bar,  'B'  54  per  cent.,  'C  58  per  cent.,  and  'D'  only  44  per  cent. 
The  forging  steel  showed  one  weld  with  only  48  per  cent.,  the 
common  soft  steel  44  per  cent.,  while  even  the  pure  basic  steel  gave 
one  test  as  low  as  59  per  cent." 

But  the,  tensile  strengths  of  the  bars  are  fairly  uniform  when 
compared  with  the  elongation.  "In  some  cases  where  the  break 
took  place  away  from  the  weld,  the  elongation  was  nearly  up  to 
the  standard."  The  elongation  test  of  a  basic  open-hearth  steel 
of  low  carbon  gave  greater  elongation  in  welded  pieces  than  in  the 
natural  bar;  "but  in  the  other  pieces  the  stretch  was  low  and  the 
fracture  so  silvery  that  it  was  plain  the  structure  of  the  bar  had 
been  ruined.  In  most  cases  where  the  test  bar  broke  in  the  weld, 
the  pieces  parted  at  the  surfaces  of  contact,  showing  that  no  true 
union  had  taken  place;  one  or  two  fractures  were  homogeneous, 
but  they  showed  the  coarse  crystallization  that  follows  over- 
heating." 2 

1  Iron  Age,  May  5,  1904.         2  "  Metallurgy  of  Iron  and  Steel,"  Wm.  Campbell. 


IRON 


Welding  Tests  of  the  Royal  Prussian  Testing  Institute1 


Kind  of  metal 

Ultimate  strength 
Ib.  per  sq.  in. 

Per  cent,  elonga- 
tion in  200  mm. 
=  7.87" 

Per  cent,  of 
reduction  of  area 

Average 
of  6  tests 
natural 

Average 
of  9  tests 
welded 

Average 
of  6  tests 
natural 

Average 
of  9  tests 
welded 

Average 
of  6  tests 
natural 

Average 
of  9  tests 
welded 

Medium  O.  H.  steel  . 
Soft  O.  H.  steel  .... 
Puddled  iron  

72110 
64570 
57890 

41820 
45800 
47080 

20.8 

25.1 

22.2 

3-2 
5-i 
7-7 

34-9 
44-7 
39-5 

4-5 
10.5 
14.0 

These  results  agree  substantially  with  those  of  Campbell. 
The  lowest  result  for  soft  steel  was  33  per  cent.,  the  average  71. 

The  lowest  result  for  medium  steel  was  23  per  cent,  the 
average  58. 

The  lowest  result  for  puddled  iron  was  62  per  cent.,  the  aver- 
age 81. 

These  results  confirm  the  general  impression  that  puddled 
iron  is  the  best  iron  for  welding.  Contrary  to  on£  authority  who 
says  that  iron  before  puddling  welds  more  easily  because  of  the 
presence  of  the  slag  in  the  iron. 

The  welding  test2  is  occasionally  specified  in  this  country  on 
account  of  the  common  use  of  welds  in  structural  work.  Two 
iron  bars  of  the  metal  under  test,  of  about  i  inch  section,  are 
scarfed,  heated  to  white  heat,  and  joined  without  flux.  The 
joint  is  worked  with  an  8-  or  lo-pound  hammer,  and  brought 
down  to  unit  section.  It  is  cooled  without  chilling.  This  bar 
is  then  tested  for  tensile  and  elastic  strength;  and  a  similar  weld 
is  half  cut  open,  bent  until  fractured,  and  examined  for  structure. 
Results  of  Tests  by  Prof.  Bauschinger 


Kind 

Section,  sq.  in. 

Ratio  of  strength  at  weld  to 
strength  of  bar,  per  cent. 

Soft  steel  and  ingot  iron. 
Wrought  iron  

0.15  tO   2.00 
O.I5  tO  2.OO 

89,  mean,  57  to  105,  range 
95,  mean,  83  to  102,  range 

1  Journal  of  the  Iron  and  Steel  Institute,  Vol.  I,  1883,  p.  425. 

2  Transaction  of  the  American  Institute  Mining  Engineers,  Vol.  II,  p.  628. 


WELDING 


Welds  made  with  steam  hammer  were  10  per  cent,  stronger  for 
mild  steel  and  5  per  cent,  stronger  for  wrought  iron  on  the 
average  than  hand  welds. 

Results  of  Tests  by  W.  C.  Unwin1 


Percentage  of 

Ratio  of  strength  at  weld  t 

o  strength  of  bar,  per  cent. 

Carbon 

Series  A 

Series  B 

o-75 

.00 
.00 

59 
76 

5° 
89 

68 

84 
"3 

•15 

•25 

75 
75 

117 
86 

Results  of  Tests  by  David  Kirkaldy  &  Son2 


Kind 

No. 

of 
tests 

Size  of  test  bar, 
inches 

Ratio  of  strength  at  weld  to 
strength  of  bar,  per  cent. 

Mean 

Range 

Electric  weld  

*7 

1.129  diam. 

89.1 

Smith  weld 

19 

1.116  diam. 

89-3 

Steel  bolts,  welded  .  . 

28 

|  to  2\  diam. 

75-1 

71.5  to  88.8 

Iron  bolts,  welded  .  .  . 

181 

\  to  2\  diam. 

73-8 

61.7  to  88.2 

Iron  tie-  bars,  welded. 

18 

i^  to  3.13  diam. 

59 

37  to  74-2 

Iron  tie-bars,  welded. 

10 

2.5x(.24  to  68) 

76.7 

Iron  plates,  welded  .  . 

7. 

iox.87  to  6x  i.  ii 

65-5 

57.7  to  83.9 

Iron  chain  links  

1086 

T\j-  to  2  (area  turned) 

86.4 

72.1  to  95.4 

Bar  plate,  welded.  .  . 

14 

\  to  i|  thickness 

68.8 

52.6  to  82.1 

1  "Testing  of  Materials  of  Construction,"  1899. 

2 "Strength  and  Properties  of  Materials,"  W.  G.  Kirkaldy,  1891. 


PLATINUM  15 

Conclusions. — Holley1  gives  three  conclusions  concerning 
iron: 

"  i.  None  of  the  ingredients  except  carbon  in  the  proportions 
present  seems  very  notably  to  affect  the  welding  by  ordinary 
methods. 

"2.  The  welding  power  by  ordinary  methods  is  varied  as 
much  by  the  amount  of  reduction  in  rolling  as  by  the  ordinary 
differences  in  composition. 

"3.  The  ordinary  practice  of  welding  is  capable  of  radical 
improvement,  the  most  promising  field  being  in  the  direction 
of  welding  in  a  non-oxidizing  atmosphere." 

He  gives  his  maximums  for  the  impurities  as  follows:  P, 
0.317;  S,  0.015;  Si,  0.321;  Mn,  0.097;  Cu,  0.45;  Ni,  0.34; 
Co,  o.  ii ;  slag,  2.262. 

Campbell's  deductions  are: 

"i.  With  the  exception  of  manganese  in  small  proportion, 
the  usual  impurities  in  steel  reduce  its  welding  power  by  lowering 
the  critical  temperature  at  which  it  becomes  coarsely  crystalline. 

"2.  A  small  content  of  manganese  aids  welding  by  preventing 
crystallization. 

"3.  Only  the  purest  and  softest  steels  can  be  welded  with 
any  reasonable  assurance  of  success. 

"4.  The  confidence  of  a  smith  in  his  own  powers  and  his 
belief  in  the  perfection  of  the  weld  is  no  guarantee  that  the  bar 
is  fit  to  use." 

According  to  Kent:2  "No  welding  should  be  allowed  on  any 
steel  that  enters  into  structures." 

PLATINUM 

Though  a  rare  metal,  being  at  this  writing  more  expensive 
than  gold,  platinum  is  much  used  for  analytical  apparatus. 
Between  the  years  1827-44  it  was  used  by  the  Russian  govern- 
ment for  coinage.3  But  it  is  now  largely  made  into  tubes,  wire, 

1  "The  Strength  of  Wrought  Iron  as  Affected  by  its  Composition  and  its  Re- 
duction in  Rolling."     Transactions  American  Institute  Mining  Engineers,  Vol.  VI,  p. 
101. 

2  "Mechanical  Engineer's  Pocket  Book." 

3  Roscoe  and  Schorlemmer,  "Treatise  on  Chemistry,"  Vol.  II,  p.  1350. 


1 6  WELDING 

crucibles,  receptacles,  etc.,  to  be  subjected  to  high  temperature 
and  to  come  in  contact  with  various  acids  and  alkalies  necessary 
for  rock  analysis;  also  for  leading-in  wires  for  incandescent 
lamps  and  for  sparking  points  for  electrical  apparatus. 

Platinum  melts  at  1760  deg.  Cent.,  is  seventh  in  the  mallea- 
bility scale  and  first  in  ductility  (Prechtl).  Heated  in  presence 
of  oxygen,  it  begins  to  lose  weight  at  800  deg.  Cent.  It  absorbs 
hydrogen  when  heated  and  gives  it  off  again  on  cooling,  and  its 
surface  becomes  rough.1  Like  iron,  it  is  highly  weldable;  best  at 
white  heat,  though  also  at  a  dull  red.  It  does  not  oxidize  in  the 
air,  hence  needs  no  flux,  though  the  surfaces  should  be  polished. 

The  need  for  welding  platinum  sometimes  arises,  as  in  the 
case  of  analysis  tubes  made  of  sheet  platinum,  the  joining  of  tubes, 
wires,  etc.,  and  the  fabrication  of  apparatus  and  the  insertion  of 
patches  in  burnt-out  crucibles. 

Before  a  flame  intense  enough  to  melt  the  metal  had  been 
discovered,  the  platinum  refiner  took  advantage  of  the  welding 
property  in  making  his  ingot.  Sponge  platinum,  resulting  from 
the  last  stage  of  refining,  was  heated  to  redness.  It  was  then 
pressed  strongly  together  to  form  a  cake.  The  cake  was  heated 
to  white  heat  and  hammered  to  a  compact  ingot.2 

The  oxy-hydrogen  blast  was  applied  to  the  heating  process 
about  1847  by  Dr.  Hare,  of  Philadelphia;  and  later  the  hammering 
was  dispensed  with  and  the  platinum  was  simply  melted  into  an 
ingot. 

Platinum  was  originally  soldered  with  gold  or  with  difficulty 
welded.  The  oxy-hydrogen  flame  makes  the  process  much 
easier,  as  the  metal  readily  melts  under  this  heat.  On  account  of 
its  tendency  to  absorb  hydrogen  and  consequent  bubbling  of 
the  surface,  it  is  necessary  to  keep  a  slight  excess  of  oxygen  in  the 
flame. 

The  oxy-acetylene  flame  would  also  answer  the  purpose, 
though  it  would  be  necessary  to  keep  a  considerable  excess  of 
oxygen  in  the  flame.  Carbon  from  the  acetylene  would  rapidly 
attack  the  platinum. 

I  am  indebted  to  Mr.  E.  A.  Colby,  of  Baker  &  Co.,  platinum 

1  Roscoe  and  Schorlemmer,  "Treatise  on  Chemistry,"  Vol.  II,  p.  1350. 

2  Encyclopaedia  Britannica,  Vol.  XIX. 


PLATINUM  17 

refiners,  for  the  subjoined  special  information,  which  covers 
points  hitherto  untouched  in  the  literature  of  platinum  and  its 
allied  metals. 

"The  oxy-acetylene  flame  can  undoubtedly  be  used  for  the 
welding  of  platinum,  but  is  not  by  ourselves  for  the  reason  that 
the  temperature  available  is  far  in  excess  of  that  necessary,  and 
lack  of  experience  leaves  us  in  doubt  as  to  the  effect  of  the  by- 
products upon  the  metal  from  the  acetylene  flame.  We  consider 
the  oxy-hydrogen  flame  far  safer  and,  as  the  heat  is  not  so  con- 
centrated, it  is  more  useful  where  large  surfaces  are  to  be  treated. 
Care,  however,  must  be  exercised  to  have  the  component  gases 
(hydrogen  and  oxygen)  present  in  approximately  the  necessary 
amounts  for  perfect  combustion.  Platinum  takes  up  hydrogen 
at  high  temperatures  and  becomes  more  or  less  brittle,  depending 
upon  the  amount  of  hydrogen  retained. 

"No  flux  is  required  in  the  welding  of  platinum  or  of  other 
metals  of  the  same  group,  osmium  excepted. 

"For  the  same  section,  the  strength  of  the  weld  is  undoubtedly 
weaker  than  that  of  the  body  of  the  metal.  Just  how  much 
weaker  we  cannot  state  from  observation,  but,  as  a  welded  joint 
is  not  submitted  to  the  same  mechanical  working  as  the  body  of 
the  metal,  its  strength  is  not  to  be  considered  as  equivalent. 
In  practice,  however,  the  welded  portion  is  slightly  increased  in 
section  over  the  body  of  the  metal,  and  under  these  conditions 
there  is  no  material  difference  in  the  strength. 

"  Iridium,  osmium,  and  other  metals  of  the  platinum  group, 
when  present  in  small  quantities,  do  not  apparently  increase  the 
difficulty  of  effecting  a  joint,  but  the  strength  of  the  joint  is  con- 
siderably less,  as  alloys  of  platinum  and  members  of  that  group 
become  more  and  more  brittle  with  increase  of  the  foreign  sub- 
stances. No  difficulty,  however,  is  experienced  in  welding 
iridio-platinum  containing  as  high  as  30  per  cent,  iridium. 
Additions  of  even  minute  quantities  of  osmium  to  an  alloy  of 
this  composition,  however,  make  it  extremely  difficult  to  obtain 
satisfactory  results. 

"Platinum  can  be  united  to  various  other  metals,  such  as 
copper,  nickel,  etc.,  but  it  is  an  open  question  as  to  whether  the 
union  can  be  considered  as  a  true  welding.  Undoubtedly,  an 


1 8  WELDING 

alloy  is  formed  of  the  two  metals  at  the  surface  of  contact  possess- 
ing sufficient  mechanical  strength  for  the  purposes  for  which 
such  welds  are  used.  The  only  illustration  of  welds  of  this  charac- 
ter are  to  be  seen  in  the  construction  of  the  ordinary  incandescent 
lamp,  in  which  the  copper  wires  attached  to  the  filaments  are 
joined  to  the  platinum  wires  sealed  in  the  glass  by  fusing  a  piece 
of  copper  onto  the  end  of  the  platinum  wire.  This  operation  is 
conducted  in  automatic  machines,  and  has  proven  very  satisfac- 
tory for  the  purpose." 

GOLD 

Gold  is  the  most  easily  weldable  of  all  the  metals.  Like  lead, 
it  can  be  welded  cold  and,  provided  it  is  free  from  certain  impuri- 
ties, it  can  be  joined  at  all  temperatures.  Gold  is  generally  placed 
first  in  tables  of  malleability  and  ductility.  These  properties 
are  destroyed  by  certain  impurities,  notably  antimony,  arsenic, 
and  bismuth.  One  part  of  bismuth  in  1,920  parts  gold  is  alone 
sufficient  to  interfere  with  the  working  properties  of  gold. 

Pure  gold  melts  at  1062  deg.  Cent,  and  will  not  oxidize  at 
any  temperature.  Hence  the  surface  will  be  clean  and  weldable. 
The  welding  property  is  very  apparent  with  gold  leaf,  which  must 
not  be  allowed  to  fold  on  itself  lest  the  surfaces  stick  together. 
Gold  fillings  in  dentistry  are  made  by  the  cold  welding  of  gold 
leaf. 

Pure  gold  is  soft  and  is  seldom  used  in  the  arts.  To  render  it 
strong  and  durable  for  coinage  and  jewelry,  it  is  alloyed  with  cop- 
per and  sometimes  with  silver.  Thus  the  gold  coins  of  Great 
Britain  contain  eleven  parts  gold  and  one  part  copper.  Those 
of  France  and  the  United  States  nine  parts  gold  and  one  part 
copper.  For  jewelry  both  copper  and  silver  are  used,  the  purity 
of  an  alloy  being  designated  by  the  number  of  carats  of  gold  in  a 
total  of  24  carats. 

The  gold  of  coinage  and  jewelry  cannot  be  joined  without  a 
flux.  The  flux  may  be  boracic  acid  or  a  solution  of  zinc  chlorid 
and  water.  In  the  making  and  repairing  of  gold  jewelry  a  mouth 
blowpipe  is  used  for  small  and  delicate  work,  and  for  larger  pieces 
a  gas  blowpipe  with  a  foot-pump  air-blast  or  compressed  air. 


SILVER  19 

The  flux  mentioned  is  used  in  case  the  surfaces  oxidize  when 
heated.  If  the  gold  is  so  alloyed  as  to  be  hard  up  to  the  melting 
point,  the  weld  will  be  a  melt-weld.  Low-carat  alloys  melt 
considerably  lower  than  pure  gold.  Hence  the  melt-weld  would 
be  made  at  about  the  temperature  that  high-carat  alloys  would 
be  plastic  enough  to  weld. 

Gold  can  also  be  readily  welded  by  electricity. 

For  ordinary  cheap  and  quick  joining  in  jewelry,  gold  is 
soldered  with  soft  solder,  a  mixture  of  two  parts  tin  and  one  part 
lead..  The  flux  is  a  solution  of  zinc  chlorid  in  water.  Such  a 
joint  is  condemned  by  the  best  jeweling  practice:  the  joint  is  not 
strong;  it  is  a  different  color  than  the  gold;  the  solder  is  apt  to 
destroy  the  strength  of  the  gold  at  the  joint. 

The  following  table  of  hard  solders,  given  by  Gee,1  are  yellow 
alloys  of  high  melting  point  and  make  strong  solders : 


Kind 

Fine  gold 

Fine  silver 

Copper 

Best  solder  

12* 

41 

3 

Medium   solder. 

10 

6 

4 

Common  solder. 

81 

61 

5 

These  alloys  are  rolled  into  ribbons  and  cut  up  into  "pallions," 
or  may  be  applied  in  dust  made  by  filing.  A  description  of  the 
soldering  of  gold  would  properly  belong  to  a  treatise  on  the 
goldsmith's  art. 


SILVER 

Silver  is  also  a  metal  of  history.  The  ancient  Greeks  knew 
of  it  as  the  metal  electrum,  an  alloy  of  gold  and  silver,  of  a  brilliant 
pink-whiteness.  Silver  is  now  used  largely  as  a  silver-gold  or 
silver-copper  alloy,  in  which  the  gold  or  copper  is  present  in 
approximately  10  per  cent.  Only  rarely  is  the  pure  metal  used, 
as  for  filigree  work  or  for  alkali  retainers. 

Pure  silver  melts  at  960  deg.  Cent.,  and  is  commonly  placed 

1  "The  Goldsmith's  Handbook,"  G.  E.  Gee,  p.  136. 


2O  WELDING 

second  in  tables  of  ductility  and  malleability.  It  does  not 
oxidize  in  air  when  heated.  All  of  these  qualities  point  to  the 
supposition  that  it  is  readily  weldable.  But  though  pure  silver 
is  made  into  filigree  work,  it  is  always  soldered.  The  common 
alloy  for  jewelry  being  a  combination  with  copper  would  suggest 
at  once  that  soldering  or  brazing  is  necessary.  In  recent  years, 
however,  silver  has  been  successfully  joined  in  the  electric  welder, 
both  to  itself  and  to  other  metals.  Because  of  its  high  heat  and 
electric  conductance  it  requires  more  current,  as  is  also  the  case 
with  copper. 

The  joining  of  silver  to  silver  is  effected  in  jewelry  shops  with 
a  mouth  or  gas-air  blowpipe  and  with  fine  silver  as  a  solder. 
Other  solders  are  alloys  of  silver  and  copper;  silver,  copper,  and 
zinc ;  and  silver,  copper,  zinc,  and  tin.  These  alloys  are  given  in 
order  of  their  melting  points,  the  most  refractory  first.  The 
flux  is  borax. 

It  would  be  well  to  bear  in  mind  that  tin  is  even  more  harmful 
to  the  working  properties  of  silver  than  it  is  to  gold  and  aluminum. 
Even  fumes  of  tin  will  alloy  with  silver  and  make  it  brittle.  For 
this  reason  tin  should  not  be  used  in  solder. 


ALUMINUM 

Aluminum  is  one  of  the  youngest  of  the  metals.  It  was 
discovered  by  Woehler  in  1827.  At  first  its  considerable  expense 
prevented  its  being  generally  used.  About  1889,  however,  the 
discovery  of  new  processes  for  its  reduction  from  bauxite,  etc., 
cheapened  aluminum,  so  that  it  has  become  a  commercial  metal. 
Since  then  the  expiration  of  the  patents  covering  many  of  the 
reduction  processes  has  brought  the  price  still  lower. 

Fairly  pure  aluminum  is  plastic  at  ordinary  temperature, 
being  sixth  in  ductility  and  second  in  malleability.1  It  melts 
at  655  deg.  Cent.;  its  plasticity  increases  with  heat  up  to  about 
600  deg.  Cent.,  when  it  becomes  hot  short,  and  will  crumble 
under  the  hammer.  It  is  easiest  to  work  between  350  and  400 
deg.  Cent.  Its  tensile  strength  runs  from  about  14,000  pounds 

1  Aluminum  Company  of  America. 


ALUMINUM  21 

per  square  inch  for  cast  bars  up  to  50,000  pounds  per  square 
inch  for  rolled  metal  and  wire. 

It  was  at  first  thought  that  its  lightness  (sp.  gr.  2 . 6)  was  its 
most  valuable  property.  But  the  experimenters  soon  found  that 
it  formed  valuable  alloys.  The  aluminum  bronzes,  aluminum- 
iron  (about  7  per  cent.),  and  some  of  the  three-  and  four-metal 
aluminum  alloys  were  found  to  be  good  metals  for  castings  for 
bearings,  and  in  many  instances  will  eventually  displace  brass, 
bronze,  and  even  steel. 

Aluminum  has  two  natural  disadvantages.  It  is  electroposi- 
tive and  it  is  difficult  to  weld  or  solder.  As  late  as  1903,  one  of 
the  prominent  periodicals1  said  editorially:  "Undoubtedly  the 
man  who  discovers  a  good  aluminum  solder  will  make  his 
fortune,  for  it  is  the  want  of  this  accessory  that  seriously  hinders 
the  development  of  aluminum  manufactures." 

Pure  aluminum  does  not  oxidize  at  ordinary  temperature, 
but  when  heated  becomes  coated  with  a  thin  film.  This  film 
is  presumably  oxid,  though  it  is  so  thin  that  not  enough  of  it  can 
be  gathered  for  analysis.  It  adheres  closely,  is  rapidly  replaced 
when  scraped  off,  and  does  not  easily  flux  away.  This  film 
covers  impure  aluminum  at  ordinary  temperature,  and  it  is 
claimed  that  aluminum  alloys  of  small  percentage  are  troubled 
with  the  surface  film.  In  pouring  for  aluminum-iron  castings 
there  must  be  only  one  flow:  the  molten  metal  is  encased  in  a 
skin  which  retards  it,  and  would  hinder  the  union  of  two  streams 
in  the  mold. 

Being  electropositive  to  all  other  metals  used  in  the  arts, 
aluminum  soldered  joints  are  troublesome.  Electrolytic  action 
sets  in,  especially  when  the  joint  is  in  contact  with  water,  and  the 
metal  at  the  joint  disintegrates.  For  this  reason  soldered  joints 
are  unsatisfactory. 

Many  solders  for  this  metal  have  been  recently  patented. 
M.  U.  Schoop  mentions  his  collection  of  50  as  being  incomplete. 
Most  of  these  inventions  specify  a  flux  that  will  remove  the  trou- 
blesome film.  The  solder  is  generally  an  alloy  of  aluminum  with 
zinc,  tin,  lead,  nickel,  copper,  or  silver,  or  any  two  or  more  of 
these  metals  in  varying  proportion.  The  softer  of  these  solders 

1  Iron  Age,  Dec.  31,  1903. 


22  WELDING 

are  fluxed  on  with  zinc  chlorid,  mercuric  chlorid,  tallow,  etc. ;  the 
harder  solders  are  fluxed  with  fluorspar,  borax,  lithium  chlorid, 
etc.1 

Dr.  Richards  has  invented  a  self-fluxing  solder  of  a  tin  and 
phosphorus  alloy.  The  phosphorus  either  reduces  or  dissolves 
the  film  that  protects  the  aluminum  surface,  and  the  tin  alloys 
with  the  clean  surface.  This  solder  is  extensively  used.  The 
present  composition  of  this  solder  is.  29  parts  tin,  n  zinc,  i 
aluminum,  and  i  phosphor- tin.2 

M.  U.  Schoop,  who  has  also  done  considerable  research  work 
in  soldering,  has  patented  a  flux.  It  is  a  mixture  of  fluorides  of  cal- 
cium, potassium,  or  boron  and  the  chlorids  of  alkali  metals,  and 
is  covered  by  British  Patent  No.  24283,  Nov.  26,  1908. 3  This 
flux  may  be  used  before  soldering  or  the  cleaned  metal  may  be 
welded  without  soldering. 

The  softer  solders  are  often  too  weak  for  good  work. 
All  of  the  solders  seem  liable  to  electrolysis.  The  flux,  in  a 
general  way,  may  vary  in  constitution,  should  not  contain 
water,  and  should  have  a  moderately  high  melting  point.  It 
should  attack  the  film,  but  not  the  metals.  Apparently  none  of 
the  solders  can  be  guaranteed  to  last  indefinitely  on  account  of 
electrolysis. 

Prof.  O.  P.  Watts,4  of  University  of  Wisconsin,  says:  "There 
has  been  considerable  trouble  with  solders  containing  tin  and 
possibly  with  some  others.  In  some  cases  destruction  may  have 
been  due  to  electrolytic  action,  but  in  others  it  appears  to  be  due 
to  a  slow  diffusion  of  the  tin  in  the  solid  state,  resulting  in  the  for- 
mation of  a  layer  of  a  very  brittle  alloy  of  aluminum  and  tin,  so 
that  the  joint  breaks.  This  is  a  slow  action  and  may  require 
a  year  or  more  for  its  completion." 

Aluminum,  as  can  be  guessed  by  its  properties,  is  a  weldable 
metal,  but  the  tenacious  film  prevents  the  natural  flow.  Accord- 
ingly, a  flux  such  as  suggested  by  Schoop  is  used  to  clean  the 
surfaces.  The  pieces  of  metal  to  be  welded  cannot  be  heated 
above  about  600  deg.  Cent.,  because  they  will  be  hot-short. 

1  "Die  Gewinnung  des  Aluminiums,"  A.  Minet. 

2  The  Metal  Industry,  1906,  p.  22. 

3  Electrochemical  and  Metallurgical  Industry,  Jan.,  1909. 
*  Special  Information. 


ALUMINUM  23 

In  1906,  W.  C.  Heraeus,1  of  Hanau  a.  M.,  exploited  a  method 
of  welding  aluminum  that  resembles  the  smith's  treatment  of 
malleable  iron.  It  appears,  however,  that  Heraeus'  discovery 
was  antedated  by  the  work  of  Mrs.  Emme  of  this  country,  who 
welded  aluminum  without  melting  it  as  early  as  1897.  Mrs. 
Emme  sued  Heraeus  for  infringement  of  patent  in  1902,  won  her 
case,  and  was  afterward  bought  out  by  him.2  The  method  as 
described  by  M.  Minet3  is  as  follows:  The  two  pieces  of  alum- 
inum to  be  welded  are  polished  carefully  around  the  ends,  and 
the  surfaces  to  come  in  contact  are  polished.  They  are  then 
heated  with  an  oxy-hydrogen  blow-pipe  or  Bunsen  flame  to  the 
proper  temperature,  400  deg.  C.  When  this  correct  tempera- 
ture is  reached,  the  two  pieces  are  pressed  against  each  other 
and  are  hammered  and  worked  as  in  ordinary  welding,  the  tem- 
perature meanwhile  being  kept  the  same.  The  metal  flows 
together  at  the  weld.  The  success  of  the  operation  depends  on 
heating  in  a  complete  reducing  flame  to  keep  the  surfaces  bright 
and  on  maintaining  the  proper  temperature.  It  would  take  a 
skilled  workman.  Upon  cooling  it  will  be  found  that  the  joint 
will  withstand  concussion  tests  and  sharp  changes  of  tempera- 
ture. Dick  patented  a  somewhat  similar  process  in  1900. 

The  limitation  of  this  practice  in  welding  is  obvious.  It  is 
not  easy  to  keep  the  metal  ends  in  a  reducing  atmosphere,  yet 
they  will  oxidize  rapidly  at  welding  heat  in  presence  of  oxygen. 
And,  besides,  aluminum  is  a  rapid  conductor  of  heat  and,  like 
copper,  the  heat  will  travel  from  the  joint  unless  the  flame  is 
very  hot. 

Cowper-Coles  has  also  done  good  work  in  welding  aluminum. 
He  has  devised  a  machine  in  which  the  bars  of  aluminum,  cleaned 
and  faced  off  square,  are  placed  and  clamped.  -  The  bars  are 
heated  with  a  benzene  lamp,  and  when  at  the  plastic  point  are 
squeezed  together  until  the  metal  at  the  joint' forms  a  considerable 
blob  and  the  oxid  has  been  forced  out  of  the  junction.  The 
weld  is  then  quickly  quenched  with  a  jet  of  water  and  at  the 
same  time  a  screen  shuts  off  the  flame.  This  contrivance  of  the 
inventor's  makes  a  weld  that  does  not  have  to  be  worked. 

1  Iron  Age,  Nov.  22,  1900. 

2  Special  information. 

3  "Die  Gewinnung  des  Aluminiums,"  A.  Minet. 


24  WELDING 

Schoop's  method  is  not  dissimilar  to  these  three  just  described; 
only  he  cleans  the  oxid  with  a  dissolving  flux  before  welding. 
Thus  his  process  does  away  with  the  difficulty  of  cleaning  the 
metal  and  keeping  it  clean;  the  rapid  conduction  of  heat  is  still  a 
difficulty. 

This  latter  property  of  aluminum,  its  high  heat  conductivity, 
is  of  least  consequence  in  the  oxy-acetylene  welding  process, 
where  the  estimated  temperature  of  the  flame  is  3600  deg.  Cent. 
This  welding  process  is  especially  adapted  to  aluminum,  takes 
less  time,  and  is  sure.  The  metal  pieces  need  no  preliminary 
cleaning,  though  if  the  body  of  the  pieces  is  large,  as  with  motor 
cases,  it  is  best  to  heat  the  whole  casting  over  a  gas  flame.  This 
because  of  the  expansion  and  the  rapid  conducion  of  heat  from 
the  fresh  weld.  The  operator  plays  his  flame  directly  on  the 
fracture,  using  a  small  melt  bar  of  aluminum  to  fill  up  the  break 
and  to  reinforce  the  weld.  Aluminum  melts  and  behaves  like 
solder  under  the  flame.  The  operator  gets  a  good  melt  at  the 
break  and  works  the  soft  metal  in  and  out  with  the  end  of  his  melt 
bar.  This  prevents  the  solidification  of  any  of  the  oxid  film  in 
the  body  of  the  piece. 

This  weld  gives  a  cast  aluminum  reinforcement  that  is  stronger 
than  the  body  of  the  piece  because  it  can  be  reinforced.  There 
is  no  reason  why  this  system  of  welding  aluminum  cannot  be 
applied  in  all  instances  where  aluminum  is  to  be  welded.  There 
are  two  precautions  necessary.  Aluminum  melts  at  655  deg. 
Cent. ;  the  temperature  of  the  flame  is  at  least  2000  deg.  So  the 
operator  must  take  care  that  he  does  not  get  his  metal  too  hot, 
or  it  will  run  away  from  the  weld.  (In  the  case  of  mending  motor 
cases,  the  fracture  is  placed  in  a  horizontal  position  and  backed 
with  asbestos  paper.)  Also,  the  operator  should  not  use  the  cus- 
tomary high-oxygen  flame.  If  he  does  his  aluminum  will  scum. 

As  for  strength  of  the  welded  joint,  Cowper-Coles,1  who  tested 
twelve  consecutive  welds  of  bars,  claimed  that  the  metal  had  not 
deteriorated.  All  of  the  bars  broke  outside  of  the  weld,  and  also 
outside  of  the  range  of  high  heating.  There  is  no  doubt,  how- 
ever, that  working  the  metal  at  the  weld  is  advantageous,  just  as  it 
is  with  iron,  etc. 

1  Electrochemist  and  Metallurgist,  Nov.,  1903. 


COPPER  25 

Conclusion. — From  the  foregoing,  it  is  plain  that  aluminum 
articles  must  be  either  welded  or  riveted — not  soldered.  It  is 
likely  that  the  manufacturers  will  soon  begin  to  use  this  welding 
property  of  aluminum  more  extensively.  Riveted  ware  is 
unsatisfactory,  because  the  metal  is  too  soft  unless  alloyed.  From 
the  fabrication  of  kitchen  ware  to  the  building  up  of  light,  strong 
metal  frames,  such  as  for  automobiles,  welds  would  be  ideal  joints. 

COPPER 

Copper  is  one  of  the  oldest,  if  not  the  very  oldest,  metals  of 
history.  It  was  used  almost  entirely  as  an  alloy  with  tin  or  zinc, 
until  recent  times.  The  aborigines  of  North  America,  however, 
found  the  pure  metal  already  smelted  for  them  on  the  shores  of 
Lake  Superior;  and  the  tools  they  used  we  find  to-day,  made  of 
nearly  pure  metal,  mistakenly  said  to  be  "  tempered  by  a  lost 
process." 

Pure  copper  melts  at  1080  deg.  Cent.,  is  fourth  in  ductility,  and 
sixth  in  malleability.1  If  free  from  certain  impurities,  such  as 
sulphur  and  carbon,  it  becomes  plastic  above  red  heat.  Under  an 
oxidizing  flame  it  will  burn  or  scale,  and  part  of  the  scale  will  be 
absorbed  by  the  metal  surface. 

It  is  a  curious  fact  that,  though  copper  is  a  weldable  metal,  as 
appears  from  its  properties,  it  is  hardly  ever  welded.  The 
common  method  of  joining  copper,  brass,  and  bronze  has  always 
been  to  solder,  braze,  or  rivet  the  pieces.  The  welding  property  is 
occasionally  mentioned,2  but  most  metal  workers  are  ignorant 
of  the  possibility.  While  the  effect  of  impurities  on  the  welding 
property  appears  not  to  have  been  gone  into,  we  may  presume 
that  the  same  substances  that  cause  red  shortness  and  assist  in 
oxidation  are  also  detrimental  to  welding;  and  that  electrolytic 
and  Lake  copper,  being  nearly  pure,  are  also  most  weldable. 
" Over-poled"  copper,  containing  carbon,  and  copper  smelted 
from  sulphid  ores  are  red-short,  and  generally  unworkable. 

The  fact  that  the  welding  of  copper  is  almost  an  unknown  art 
is  strikingly  shown  by  the  fact  that,  in  reply  to  the  query  of  a 

1  Prechtl. 

2  American  Machinist,  Oct.  23,  1902;  Schnabel's  Metallurgy,  p.  i. 


26  WELDING 

correspondent,  the  editor  of  a  leading  technical  publication 
recently  replied  as  follows:  That  copper  was  not  weldable; 
that  it  flew  to  pieces  if  hammered  when  hot;  and  that  it  burned 
rapidly  at  welding  heat,  and  would  not  braze  perfectly. 

The  flux  for  copper  welding  usually  contains  borax  or  boracic 
acid  and  a  phosphate  salt.  One  flux  recommended  is  two  parts 
sodium  phosphate  and  one  of  boracic  acid;1  another  is  one  part 
yellow  potassium  prussiate  and  twenty  parts  of  borax.2  A 
pinch  of  rosin  is  sometimes  added  to  the  flux.  When  using  a 
phosphate  in  the  flux  care  must  be  taken  not  to  bring  the  copper  in 
contact  with  free  carbon,  because  copper  phosphate  will  form  and 
will  prevent  sound  welding.3 

To  weld,  the  metal  is  heated  to  redness,  when  it  becomes 
plastic.  The  calcined  flux  is  sprinkled  on  the  surface  and  the 
pieces  are  then  joined  at  a  yellow  heat  and  hammered  together 
as  in  iron  welding.  When  using  a  phosphate  flux,  do  not  touch 
the  copper  with  coke  or  charcoal.  A  gas  or  oil  flame  is  pret- 
erable,  or  the  pieces  can  be  heated  in  an  electric  welder  or  with 
a  high-temperature  torch.  An  ordinary  hammer  and  anvil  can 
be  used,  but  on  account  of  the  rapid  conduction  of  heat  away 
from  the  joint,  a  piece  of  brick  or  stone  can  be  substituted  for 
the  anvil  and  a  wooden  mallet  for  the  iron  hammer.  Copper  at  a 
red  or  yellow  heat  is  very  plastic,  if  not  red-short.  So  it  is  well 
to  upset  the  metal  considerably  at  the  joint  to  allow  for  working 
with  the  hammer. 

Copper  is  welded  by  the  electric  process,  and  a  melt-weld  can 
be  made  with  the  hydrogen  or  acetylene  burner.  But  in  either 
case  it  has  been  shown  that  the  fibrous  structure  is  destroyed  and 
a  crystalline  joint  occurs.  As  with  wrought  iron,  the  copper  weld 
must  be  hammered  or  drawn  to  restore  the  fiber.  Copper 
welding  is  generally  considered  unsatisfactory,  soldering  and 
brazing  being  preferred,  as  either  can  be  done  below  the  critical 
temperature  of  crystallization. 

The  smith  welding  of  pure  copper  is  considered  more  difficult 
than  the  smith  welding  of  wrought  iron.  And  because  pure  copper 
is  inferior  in  strength  to  pure  iron,  it  is  unlikely  that  the  welding 

1  American  Machinist,  Sept.  25,  1902. 

2  Ibid. 

3  Ibid. 


NICKEL  27 

property  will  ever  be  generally  taken  advantage  of.  But  the 
knowledge  that  copper  can  be  smith  welded  and  that  the  welds 
can  be  made  of  100  per  cent,  strength,  may  be  occasionally 
found  to  be  useful  in  the  arts. 


NICKEL 

Nickel  is  a  metal  of  secondary  importance.  Its  principal 
use  is  in  nickel  alloys,  notably  nickel-steel,  in  plating,  in  coin- 
age, and  in  the  chemical  reductions  which  call  for  apparatus 
made  of  a  metal  of  inertness  similar  to  platinum,  but  of  greater 
cheapness. 

The  pure  metal  is  harder  than  iron,  melts  at  1451  deg.  Cent., 
slightly  below  iron,  and  is  malleable  and  ductile.  It  resembles 
iron  in  being  plastic  at  a  bright  red  or  white  heat,  and  is  readily 
weldable  at  that  temperature.  As  the  ordinary  nickel  of  com- 
merce is  quite  brittle,  due  to  its  impurities,  it  is  seen  that  it  will 
not  weld.  The  welding  property  of  pure  nickel,  however,  is  of 
importance  in  nickel  plating  and  in  making  seamed  nickel  tubes. 

One  of  the  chief  objections  to  nickel  plate  is  its  tendency 
to  scale  or  peel  off.  Electroplated  nickel-iron  cannot  be  drawn, 
bent,  or  hammered  with  safety,  and  frequent  changes  of  tem- 
perature will  also  tend  to  crack  the  nickel  surface. 

Theodore  Fleitmann,  of  Iserlohn,  Germany,  took  out  a 
patent  a  number  of  years  ago  for  making  nickel-plated  iron  by 
mechanical  means.  Sheets  of  nickel  and  iron  were  heated  to 
welding  heat  in  an  atmosphere  of  hydrogen,  after  having  been 
polished  and  fluxed.  They  were  then  welded  between  rolls, 
without  coming  in  contact  with  the  air.  By  this  method  the 
natural  tendency  of  both  metals  to  oxidize  quickly  was  prevented. 
At  the  welding  heat  the  metals  alloyed  at  the  contact  surfaces, 
and  a  plate  was  produced  that  could  be  rolled  without  detriment 
to  the  nickel  surface. 

In  1903,  Thomas  A.  Edison  took  out  a  patent  for  a  some- 
what similar  idea.  The  difference  was  that  his  nickel  was 
electrolytically  deposited,  the  plate  was  raised  to  redness  in 
hydrogen  gas  by  electric  current,  and  then  rolled.  At  first 
Edison  plated  iron  sheets  in  a  nickel  solution,  piled  them  together 


28  WELDING 

in  a  clay  or  cast-iron  retort,  and  raised  them  to  bright  redness 
in  a  hydrogen  atmosphere.  At  this  temperature  the  metals 
alloyed  and  knitted  at  contact.  They  were  cooled  below  oxidiz- 
ing temperature  in  the  same  atmosphere  before  a  new  change 
of  plates  was  admitted.  Later,  Edison  improved  his  process 
by  making  it  continuous.  The  iron,  in  a  roll,  was  passed  first 
through  a  chamber  of  hot  hydrogen,  which  reduced  all  oxids 
and  gave  it  a  fresh  surface.  From  this  first  chamber  it  passed 
into  a  cooling  chamber  of  the  same  gas,  then  through  the  nickel 
bath,  and  the  wash-tank;  thence  through  a  third  hydrogen 
chamber,  where  it  was  raised  to  welding  heat;  and  lastly  to  a 
cooling  chamber  of  hydrogen.  The  speed  was  gauged  to  allow 
each  step  of  the  operation  sufficient  time.1 

In  1905,  the  Standard  Welding  Company,  of  Cleveland, 
exhibited  tubes  of  pure  nickel  welded  electrically.  The  tubes 
were  strong  and  the  seam  was  invisible.  The  present  demand 
for  such  tubes  comes  from  automobile  makers,  rubber  manu- 
facturers for  their  end  tubes,  and  industrial  chemists  for  non- 
oxidizable  tubes,  retorts,  and  crucibles. 

WELDED  PRODUCTS 

A  great  variety  of  tools,  appliances,  and  parts  are  welded  in 
some  stage  of  their  manufacture.  Where  pieces  of  metal  are  to 
be  joined,  welding  is  the  first  resort,  soldering  a  poor  alternative. 
As  welding  is  itself  a  simple  process,  the  chief  difference  lies  in 
the  machinery  necessary  for  different  work.  In  a  work  of 
limited  scope  it  will  not  be  necessary  to  go  into  the  details  of 
the  stock  welds,  but  a  number  of  the  most  important  will  be 
mentioned. 

The  processes  of  manufacture  are  in  many  cases  adaptations 
of  the  recently  discovered  processes  of  welding.  The  electric 
process  is  far  ahead  for  repeat  or  " stock"  welding.  The  hot 
flames  are  best  for  job  work,  but  are  beginning  to  compete  with 
electricity  for  "stock"  work.  Thermit  is  used  mostly  for  job 
welding  or  repairing,  but  can  also  be  applied  to  continuous  rail 
or  pipe  joining. 

1  The  Metal  Industry,  Aug.,  1904. 


WELDED    PRODUCTS  29 

Wrought-iron  Pipe. — Pipe  welding  is  about  100  years  old, 
and  at  this  writing  the  manufacture  of  welded  wrought-irbn 
pipe  consumes  a  large  percentage  of  all  the  wrought  iron  made. 
The  first  pipe  was  heated  over  a  coke  fire  and  lap-welded  in 
sections.  After  the  Napoleonic  wars  gun  barrels  were  a  drug 
on  the  market  and  came  to  be  used  for  water  piping.  This  supply 
seemed  to  stimulate  the  demand,  and  soon  after  important  inven- 
tions began  to  assist  and  simplify  the  original  primitive  methods. 
James  Russell,  who  substituted  the  butt  for  the  lap-welded  pipe 
in  1825,  may  be  called  the  father  of  the  pipe  industry. 

Wrought-iron  pipes  are  made  in  a  number  of  ways.  The 
original  lap-weld  is  still  used  for  its  strength.  Most  pipe  is 
butt-welded  from  long  scarfs  of  iron,  heated  in  a  gas  or  coke 
oven,  bent  round,  reheated,  and  then  welded  by  being  drawn 
over  a  mandrel  and  through  a  die  of  slightly  lower  caliber  than 
the  pipe.  In  this  way  the  edges  are  squeezed  together  on  the 
outside,  while  the  mandrel  pressing  on  the  inside  completes  the 
weld.  A  recent  invention  is  pipe  made  from  a  spirally  wound 
and  welded  strip  of  iron.  Weldless  drawn-steel  tubing  is  also 
finding  a  market,  but  so  far  welded  pipe  has  proved  to  be  cheaper. 
The  process  is  now  a  continuous  one;  and  electric  welded  pipe  is 
now  on  the  market. 

Welded  pipe  is  made  in  sizes  of  from  1/8  inch  to  about  30 
inches  internal  diameter.  Larger  than  this,  it  is  generally  riveted. 
The  iron  must  be  of  very  good  quality,  quite  pure,  and  low  in 
sulphur  and  carbon.  Fifty  thousand  pounds  per  square  inch 
tensile  strength  is  as  high  as  it  is  safe  to  try  to  use,  as  stronger 
irons  than  this  give  weaker  welds.  High-carbon  irons  and  steels 
should  never  be  used  for  pipe,  though  their  initial  strength  is 
great.  Such  metal  welds  poorly  and  may  easily  pull  apart  at 
the  weld  under  great  pressure. 

Chain  Making. — Chains  made  of  iron  links  were  known  to 
the  first  smiths  or  workers  in  iron.  And  though  chain  is  now 
replaced  in  many  instances  by  lighter  and  stronger  cables,  it  is 
one  of  the  staple  iron  and  steel  products.  One  writer1  estimates 
that  in  1905  there  were  in  the  United  States  thirty  chain  mills, 
having  a  total  yearly  output  of  50,000  tons  of  chain. 

1  "The  Manufacture  of  Chain,"  L.  B.  Powell,  Iron  Age,  Jan.  5,  1905. 


30  WELDING 

The  early  chain  makers  often  welded  their  links  at  the  end,  and 
even  made  circular  links.  But  modern  practice  is  to  make  the 
link  an  oval  and  to  weld  the  stock  on  one  side  of  the  link.  The 
stock  used  varies  in  diameter  from  approximately  1/8  inch  to 
over  3  inches,  and  the  links  are  from  1/2  inch  to  a  foot  or  more 
long.  Safe  practice  limits  the  diameter  of  the  stock  from  ap- 
proximately 3/8  inch  to  2  inches,  as  sizes  smaller  are  apt  to 
burn  when  heated  and  sizes  larger  are  apt  to  weld  poorly  and 
are  unworkable. 

Chain  is  still  largely  made  by  hand,  and  requires  skill  and  care 
for  every  link.  Speed  and  a  uniform  product,  have  been  developed 
by  special  machines  in  late  years.  The  links  are  now  cut  from  a 
spring-spiral  of  the  iron,  are  heated  in  a  gas  oven,  are  welded  and 
swaged  by  a  hydraulic  press  with  die  of  suitable  shape.  Small 
chain  can  now  be  made  on  an  automatic  electric  welder. 

As  with  welded  pipe,  the  chain  iron  should  not  be  of  high  ten- 
sile strength,  about  50,000  pounds  per  square  inch,  and  should  be 
quite  pure.  The  ultimate  strength  of  a  chain  depends  on  its 
design  and  the  perfection  of  the  weld.  And  as  life  and  property 
are  constantly  at  the  mercy  of  just  one  poor  weld,  the  different 
nations  and  insurance  companies  prescribe  tests  that  are  approxi- 
mately double  what  the  chain  will  be  allowed  to  undergo  in  prac- 
tice. In  this  country  the  U.  S.  Testing  Board  and  in  Great  Brit- 
ain the  British  Admiralty  Board  and  Lloyd's  restrict  the  load  to 
50  per  cent,  of  the  ultimate  strength  of  the  weakest  link. 

Miscellaneous. — Other  stock  welds  of  importance  are  car- 
riage tires,  frames,  hub  and  axle,  and  also  spoke-and-hub.  The 
carriage  industry  is  founded  on  the  weldability  of  iron. 

Cap  screws  have  larger  heads  of  tough  steel  welded  on  by 
electricity.  There  are  children's  hoops,  printers'  chases,  three- 
ply  skate  blades,  garden  rakes,  boiler  tubing,  axe-blades,  shotgun 
barrels,  iron  rings,  wire  fences. 

The  best  grade  of  American  anvils  are  made  of  a  hard  quality 
of  steel  plate  welded  on  to  the  top  of  the  block,  while  the  anvil 
horn  is  also  welded  on.  The  best  plows  have  welded  steel  points 
to  resist  the  wear. 

Besides  these  older  products,  many  of  the  industries  which 
have  recently  sprung  up  are  using  welding  apparatus  for  making 


WELDED    PRODUCTS  31 

minor  parts  of  apparatus  and  machinery — the  joining  of  a  durable 
well-wearing  metal  on  a  softer  body,  one  metal  to  another,  or  one 
special  casting  to  another,  so  as  to  avoid  the  use  of  intricate  pat- 
terns. Ship-builders  weld  constantly,  though  it  is  bad  practice  to 
weld  a  vital  part.  Smith  welding  is  used  much  less  than  formerly 
on  manufactured  articles.  The  patent  welding  processes  are 
cheaper,  quicker,  and  safer  and  are  superseding  the  old  hand 
method. 


PART  II— ELECTRIC  WELDING 


GENERAL 

Electric  welding  processes  have  been  used  commercially  since 
about  1880,  when  Elihu  Thomson  brought  out  his  low-pressure 
resistance  machine,  invented  about  1877.  In  recent  years  several 
processes,  notably  that  of  Thomson,  have  become  widely  known 
for  their  successful  application  to  rail  welding  and  to  repeat 
welding  of  stock  pieces  in  manufactories,  such  as  wheelbarrow 
spokes,  wagon  frames,  printing  chases,  etc.  Though  the  several 
processes  in  which  electric  current  is  used  in  welding  are  unlike 
in  apparatus  and  application,  the  basic  idea  of  each  process  is  to 
produce  the  welding  heat  by  means  of  resistance  to  an  electric 
current.  The  different  processes  are: 

1.  La  Grange-Hoho  process:  resistance  being  set  up  in  an 
electrolyte. 

2.  Zerener   electric   blowpipe:  an   ordinary  electric  arc  de- 
flected by  a  magnet. 

3.  Bernardos  arc- welder:  the  metal  to  be  welded  as  the  posi- 
tive pole  and  a  carbon  negative. 

4.  Thomson   process:   in   which   internal   resistance   in   the 
metal  to  be  welded  generates  the  heat.     This  is  also  called  the 
incandescent  process. 

The  electric  welding  processes,  especially  the  latter,  have  fol- 
lowed the  adoption  of  the  oxyhydrogen,  gas,  and  oil  flames,  and 
slightly  antedate  the  oxy-acetylene  and  thermit  welding  methods. 
The  arc-welding  systems  have  followed  the  commercial  introduc- 
tion of  the  arc-light  in  1881.  The  internal  resistance  method 
was  earlier  suggested  by  the  experiments  of  Joule  and  Moissan. 
In  1856  Joule  welded  a  bundle  of  iron  wires  by  burying  them  in 
charcoal  and  heating  them  with  current.  While  in  Moissan's 
furnace  the  resistance  of  a  closed  metallic  circuit  (as  well  as  the 

3  33 


34  WELDING 

arc-furnace)  generated  the  heat  for  melting  refractory  metals  and 
for  making  alloys. 

The  Thomson  process,  the  oldest  and  most  important,  will 
here  be  last  described. 


THE  LA  GRANGE-HOHO  PROCESS 

This  process  is  well  called  the  "  water-pail  forge."  It  comes 
from  Belgium  and  has  scarcely  been  tried  out.  The  metals  to 
be  heated  are  fastened  to  the  negative  pole  of  the  circuit  and 
immersed  in  a  bath  of  an  electrolyte,  such  as  potassium  carbonate 
solution.  The  current  when  turned  on  flows  from  the  positive 
pole  through  the  solution,  and  returns  by  way  of  the  metal  piece 
as  a  negative  terminal.  The  solution  begins  to  decompose, 
depositing  hydrogen  on  the  metal  piece  in  a  thin  film.  The 
metal  piece  becomes  red-  or  white-hot,  and  is  protected  from  the 
solution  by  the  hydrogen  film.  As  soon  as  the  proper  heat  is 
reached,  as  told  by  the  color  of  the  metal,  the  pieces  are  taken  out 
of  the  solution,  and  welded  or  hammered  together  on  an  anvil 
with  a  hammer. 

The  advantage  of  this  process  is  that  the  metals  are  perfectly 
cleansed  from  grease,  dirt,  and  oxid  by  the  bath,  and  are  protected 
by  the  hydrogen  film. 

The  disadvantage  is  that  the  heat  is  not  easily  controlled. 
While  the  working  of  the  hot  metal  must  be  done  by  hand  in  the 
air  where  the  metal  will  soon  oxidize. 

This  process  is  not  likely  to  have  a  wide  industrial  application. 

THE  ZERENER  ELECTRIC  BLOWPIPE 

Werderman  applied  the  high  heat  of  the  electric  arc  to 
melting  and  welding  metals.  His  apparatus  was  an  ordinary 
flaming  arc,  the  carbons  being  inclined  toward  each  other.  The 
flame  of  the  arc  was  directed  away  in  a  point  from  the  carbons 
by  means  of  a  blast  of  air.  In  a  more  recent  development  by 
Zerener  the  repulsion  of  an  electromagnet  in  series  with  the  arc  is 
used  to  direct  the  arc  against  the  work.  The  following  points 
have  been  charged  against  this  process: 


THE    BERNARDOS   ARC-WELDING    PROCESS 


35 


1.  That  it  is  much  cheaper  than  either  the  oxy-hydrogen  or 
oxy-acetylene  flames;  because  the  initial  cost  of  the  apparatus  is 
lower  and  the  cost  of  the  energy 

used  is  less  than  the  cost  of  the 
hot-flame  gases  for  the  same 
amount  of  work  done. 

2.  That    the    flame   is   not 
easy  to  control. 

3.  That  the  flame  is  satu- 
rated, with  hot  carbon  and  car- 
bon gas  from  the  pencils.     The 
carbon    is    taken    up    by   the 
molten   metal,  which   becomes 
burnt  or  brittle. 

4.  That  the  intense  light  of 
the   arc   and   the  high  voltage 
necessary    make    the    welding 
rather  dangerous  to  the  oper- 
ator. 

5.  That  only  a  limited-sized 
flame  can  be  obtained. 

The  Zerener  arc  has  appar- 
ently never  been  tried  out  in 
this  country.  Abroad  it  is 
sometimes  used  for  welding 
rough  work,  such  as  broken 
castings  and  pieces  that  do  not 
need  to  retain  any  elasticity. 
In  spite  of  its  several  limita-  FlG-  I0--Zerener  blowpipe  apparatus, 
tions,  the  cheapness  of  operation  should  recommend  it  to  trial. 


THE  BERNARDOS  ARC-WELDING  PROCESS 

This  arc-welding  process  is  an  evolution  of  the  electric  furnace. 
In  the  electric  furnace  of  Moissan  and  others  the  electrodes  were 
both  carbon,  and  the  metal  to  be  melted  was  placed  between  the 
carbons  in  the  path  of  the  arc.  De  Meritens  substituted  the 
metal  itself  for  one  of  the  carbons;  and  later  Bernardos,  a 


36  WELDING 

Russian,  perfected  the  process.  Coffin  has  taken  out  similar 
patents  in  America.  The  Bernardos  process  has  been  known  in 
Europe  for  more  than  twenty  years,  and  has  recently  been  intro- 
duced into  this  country.  Welding  heat  is  obtained  by  the  elec- 
tric arc.  The  metal  to  be  welded  or  melted  is  the  positive 


FIG.  II. — Operator  welding  with  Bernardos  arc  process. 

pole.  The  negative  pole  is  a  carbon  pencil.  The  current  used 
is  direct,  of  100  to  300  volts,  and  600  to  1000  amperes.  The 
metal  to  be  welded  lies  on  a  metal  table  to  which  the  positive  pole 
is  clamped.  The  carbon  negative  is  placed  in  contact  with  the 
metal  and  the  current  is  thrown  on.  The  carbon  pole  is  then 


THE    BERNARDOS   ARC-WELDING    PROCESS 


37 


withdrawn  2  to  4  inches,  and  an  arc  is  sprung,  which  follows  the 
carbon  wherever  the  carbon  is  manipulated  by  the  operator.  The 
greater  part  of  the  heat  of  the  arc,  about  3500  deg.  Cent.,  is  gener- 
ated in  the  metal  or  is  reflected  back  on  the  metal  from  the  arc. 
The  apparatus  used  is  as  follows: 


FIG.  1 2.— Operator  welding  with  Bernardos  arc  process.    (Courtesy  proceedings 
of  the  Engineering  Society  of  western  Pennsylvania,  May,  1909,  C.  B.  Anel.) 

1.  Generator  of  direct  current  of  100-300  volts  and  600-1000 
amperes. 

2.  A  metal  table  on  which  to  place  the  work. 

3.  Leads,  switches,  and  controlling  apparatus  for  the  current, 
carbon  pencil. 


3  8  WELDING 

4.  Protective  apparatus  for  the  workman. 

Apparatus  and  Current. — The  Generator. — It  is  claimed 
by  the  advocates  of  this  system  that  good  results  cannot  be  ob- 
tained unless  current  of  ample  volume  and  pressure  be  used. 
Current  from  power  wires  is  generally  inadequate.  It  is  best 
to  have  a  special  dynamo  of  not  less  than  75  to  100  kw.  For 
reasons  given  below,  the  current  should  be  direct.  Where  the 
current  supplied  is  alternating,  a  direct-coupled  motor-genera- 
tor is  used  to  transform  to  direct  current.  The  motor-generator 


Shunt  Field 
with  Rheostat 


FIG.  13. — Diagram  of  Bernardos  arc  welder. 


coupling  must  be  flexible  to  prevent  the  armature  from  burning 
out.  This  generator  will  be  much  the  most  expensive  part  of  the 
apparatus — costing  more  than  all  the  other  mechanism. 

Direct  current  is  much  better  and  cheaper  than  alternating. 
As  is  well  known,  the  greatest  heat  is  found  near  the  positive  pole 
of  the  arc.  For  this  reason  the  metal  object  to  be  welded  is  made 
the  positive  pole  of  a  direct  current.  If  it  were  the  negative  pole, 
more  heat  would  be  lost  and  the  carbon  from  the  pencil  would 
enter  the  weld  and  harden  the  metal.  While  if  an  alternating 
current  were  used,  some  of  the  carbon  would  enter  the  hot  metal, 


THE    BERNARDOS   ARC-WELDING    PROCESS  39 

while  the  weld  would  not  receive  more  than  half  the  heat  of 
the  arc. 

Table,  Switches,  Controlling  Apparatus,  Carbon. — The  table 
which  holds  the  work  is  of  cast  or  wrought  iron.  The  metal 
to  be  welded  is  laid  on  the  table,  and  it  is  supposed  that  the 
contact  between  table  and  metal  will  be  sufficient  to  carry  the 
current.  If  the  piece  of  metal  is  small,  the  positive  lead  had  bet- 
ter be  clamped  directly  onto  the  metal  instead  of  the  table. 

The  switchboard  contains  a  single-throw  switch  and  a 
rheostat  connected  with  grids.  Or  the  rheostat  may  be  made  of 
water-barrels  with  insulated  sides  and  a  terminal  plate  for  a 
bottom.  The  other  terminal  is  also  a  metal  plate  suspended  over 
the  barrel.  It  is  lowered  in  and  out  of  the  water  of  the  barrel. 


Shield 
Lead 


FIG.  14. — Carbon  negative  pole  and  shield. 

The  trouble  with  barrel  rheostats  is  that  the  water  is  liable  to  boil 
over  under  continuous  usage,  while  the  barrel  hoops  will  rust  rap- 
idly. Circuit  breakers  should  be  used  to  prevent  the  armature 
from  burning  out,  in  case  'the  operator  accidentally  short-circuits 
by  touching  his  carbon  pencil  to  his  work. 

The  carbon  pencils  are  made  in  sizes  of  i/4-inch  to  i  1/2- 
inch  diameter  by  6  to  12  inches  long — of  sound  carbon.  The 
carbon  pencil  is  fixed  into  an  insulated  handle.  Midway  on  the 
handle  is  a  round  shield  to  protect  the  operator  from  the  flame 
of  the  arc  and  from  sparks  (see  Fig.  14). 

Workman's  Protective  Apparatus. — Under  this  head  come 
rubber  gloves,  a  leather  or  rubber  suit  or  apron,  a  hood  of  cloth, 
stovepipe  or  wood  for  the  head,  and  a  pair  of  glasses  for  the  eyes. 
Bear  in  mind  that  the  operator  is  manipulating  a  current  of  high 
voltage  and  also  an  arc  of  great  heat  and  dazzling  light.  A  stove- 


40  WELDING 

pipe  hood  for  the  head  is  rather  unsafe  because  of  the  danger  of 
shock.  The  eye-glasses  had  better  be  double,  of  red  and  green 
or  red  and  blue  glass,  because  the  light  is  violent. 

Practice. — In  practice  the  metal  piece  to  be  welded  is  clamped 
onto  the  metal  table.  The  positive  lead  is  also  clamped  onto 
the  table  or  sometimes  directly  to  the  metal  piece.  The  carbon 
electrode  is  pressed  against  the  metal  piece,  and  the  switch  is  then 
closed.  The  operator,  clad  in  his  insulated  clothing  and  hood, 
then  draws  the  carbon  pencil  away  from  the  piece  about  2  to  4 
inches  and  makes  the  arc.  If  the  arc  goes  out  or  is  too  intense, 
the  current  is  increased  or  diminished  at  the  rheostat. 

As  with  the  hot-flame  processes,  the  operator  now  gives  his 
arc  a  circular  movement,  taking  care  to  keep  the  pencil  at  least 
2  and  not  more  than  4  inches  from  the  work.  As  the  metal 
begins  to  melt,  he  works  it  into  the  weld  with  a  stick  of  melt  bar, 
as  in  the  oxy-acetylene  process  (see  page  97).  The  weld  may 
also  be  reinforced  with  scraps  of  the  kind  of  metal  needed.  If  the 
metal  is  brass  or  zinc,  it  is  best  to  cover  it  with  a  layer  of  the 
proper  flux. 

A  slight  variation  of  the  Bernardos  system  is  practised  in 
Sweden  in  the  welding  of  boiler  plate.  Instead  of  a  carbon 
negative,  a  bar  of  soft  steel  is  used.  The  bar  begins  to  melt  in 
about  a  minute  and  is  then  pressed  on  to  the  weld  and  the  cur- 
rent cut  off.  The  joint  of  the  two  plates  has  already  melted  and 
the  bar  acts  as  melt  bar.  The  joint  is  hammered,  and  the  arc 
is  again  sprung  and  more  of  the  bar  melted  on. 

The  details  of  manipulating  the  torch  and  metal  in  this 
process  are  not  different  from  the  hot-flame  processes.  Dif- 
ferent metals  require  different  treatment  in  heating,  fluxing, 
and  working.  Metals  that  melt  to  a  liquid  will  have  to  be  built 
up  with  a  luting  of  clay  or  bricks. 

It  is  claimed  for  the  Bernardos  process  that  the  metal  at  the 
weld  is  not  injured  by  the  heat  or  the  current  if  the  operator 
follows  directions  and  uses  common  sense.  Iron  welds  should 
not  be  brittle  or  hard  unless  the  carbon  was  originally  high. 

Samuel  McCarthy1  gave  the  results  of  comparative  tests  of 
the  tensile  strengths  of  bars  scarf-welded  and  bars  electrically 

1  "Bernardos  Arc-welding,"  read  before  the  Inst.  of  Mech.  Engineers,  England. 


THE    BERNARDOS   ARC- WELDING    PROCESS  41 

welded.  The  bars  were  of  several  different  grades  of  English 
iron  and  steel,  of  cross-section  2  by  1/2  inches  approximately. 
He  claims  an  advantage  averaging  18  1/2  per  cent,  for  the  arc- 
welded  bars  over  the  smith-welded  bars.  The  arc-welded  bars 
ran  from  73.6  to  92  per  cent,  of  the  strength  of  the  original 
stock. 

The  Bernardos  process  at  present  is  recommended  for  general 
repair  work,  such  as  boiler-plate  repairing,  broken  castings, 
cracked  parts,  etc.  The  process  is  handicapped  greatly  by  the 
violence  of  the  light  and  heat  of  the  arc,  by  the  limited  size  of  the 
flame,  and  by  the  danger  to  the  operator  from  the  high  voltage. 
As  with  the  hot-flame  process,  the  heating  effect  is  purely  local, 
and  one  part  of  the  weld  may  be  getting  cold  while  the  other 
part  is  being  welded.  Even  heating  may  be  obtained  by  pre- 
heating over  a  gas  flame;  freedom  from  shrinkage  strains  may 
be  had  by  annealing.  The  oxy-acetylene  flame  may  be  turned 
on  the  work  from  several  burners  at  once.  But  so  far  there  is 
but  one  arc  with  each  welder.  It  is  not  likely  that  two  or  more 
arcs  will  be  used  together  on  one  job;  the  only  way  to  increase 
the  size  of  the  work  to  be  welded  is  to  increase  the  carbon  pencil 
and  augment  the  current.  Such  increase  has  sharp  limitation. 

Cutting  Metals  with  Electric  Arc. — The  Bernardos  arc 
is  also  used  to  cut  metals.  Its  adaptation  to  metal  cutting  is  of 
recent  date.  The  arc  is  held  stationary  over  the  plate  until  the 
metal  is  melted  in  one  place.  This  melted  metal  is  ladled  or 
poured  out  of  the  hole  by  tilting  the  plate.  To  obtain  a  clean- 
cut  hole,  it  is  best  to  reverse  the  plate  and  complete  the  hole  from 
the  other  side.  If  the  arc  can  be  manipulated  on  a  horizontal 
plane  or  held  underneath  the  plate,  the  hot  metal  will  flow  out 
of  the  melt  hole  of  its  own  accord.  A  cut  in  the  metal  plate  is 
made  by  advancing  the  arc  along  the  line  of  cutting  as  fast  as 
the  metal  melts. 

This  cutting  property  of  the  Bernardos  arc  is  somewhat  similar 
to  the  oxy-acetylene  torch  (see  page  75).  The  arc  is  not  so  effi- 
cient as  the  acetylene  torch,  however.  The  latter  makes  a 
cleaner  and  smaller  cut  and  clears  the  metal  away  as  the  flame 
advances.  The  cutting  arc  has  been  used  to  cut  down  the  steel 
piers  of  the  Ferris  wheel,  for  thawing  the  taps  of  frozen-up  blast 


WELDING 


furnaces,  for  cutting  off  parts  of  castings,  and  also  for  mending 
cracks  in  castings. 

Mr.  Auel1  gives  the  following  table  of  data  for  the  cutting 
arc  as  approximate: 

Bernardos  Process,  Burning  Hole  in  Wrought-iron  Plate2 


Line  volts 

Amperes 

Volts  across 
rheostat 

Volts  across  arc 
including  carbon 

1  20  (open  circuit)  . 

08   . 

430 

23 

72 

102     
I  O4. 

400 
•770 

22 
2O 

81 
86 

85     
87     

1000  (kick) 
1000  (kick) 

24 

35 

60 
63 

THE  THOMSON  PROCESS 

"This  process  differs  radically  from  all  the  others  in  forcing 
through  the  metal  to  be  heated  electrically  such  volumes  of  current 
that  its  own  resistance  is  sufficient  to  bring  every  molecule  of  the 
section  traversed  by  the  current  to  the  desired  temperature."3  Cur- 
rent is  taken  from  a  lighting  or  power  circuit,  is  stepped  down 
to  the  required  3  or  more  volts  and  higher  volume,  and  is 
passed  through  a  secondary  circuit  in  which  the  greatest  resist- 
ance is  offered  by  the  pieces  of  the  metal  to  be  welded.  The 
cross-section  and  unit  resistivity  are  so  proportioned  to  the  flow 
of  current  that  the  resistance  produces  red  or  white  heat  at  the 
point  of  welding.  The  hot  metals  are  then  forced  together  and 
the  weld  is  made.  The  apparatus  necessary  are: 

1.  A  generator  of  alternating  current. 

2.  A  step-down  transformer,  carried  in  the  body  of  the  welder. 

3.  Apparatus    for    regulating    the    current,    and    sometimes 
apparatus  for  automatically  shutting  off  the  current  as  soon  as 
welding  heat  is  reached. 

1  "Arc  Welding,"  C.  B.  Auel,  Proceedings  of  the  Engineers'  Society  of  Western 
Pennsylvania,  May,  1909;  presented  before  the  Society,  April,  1909. 

2  Size  of  hole  =  if  inches  diameter  by  i£  inches  deep.     Size  of  carbon  =--i% 
by  6  inches.     Time  =  3  minutes  30  seconds  (includes  45  seconds  for  reversing  plate). 

3  Hermann  Lemp,  The  Engineering  Magazine,  Aug.,  1894. 


THE    THOMSON   PROCESS  43 

4.  Clamps  for  holding  the  metal  to  be  welded  and  to  transmit 
the  current  to  it. 

The  Thomson  process  presents  a  number  of  decided  advan- 
tages. Among  them: 

1.  It  is  at  present  the  best  all-around  welding  machine  for 
welding  continuous  runs  of  one  weld,  such  as  printers'  chases. 

2.  The  power  used  is  claimed  to  give  a  75  per  cent,  heat 
efficiency;  the  power  is  used  only  as  long  as  needed,  and  is  turned 
off  as  readily  as  the  hot-flame  welding  burners. 

3.  The  heating  is  rapid,  even,  entirely  local,  and  is  under 
control. 

4.  There  is  no  excessive  heating  as  with  the  electric  arc; 
hence  no  excessive  oxidation  or  decarbonizing  of  the  metal. 

5.  The  clamps  hold  the  work  in  accurate  alignment  and 
furnish  pressure  enough  to  squeeze  well  the  hot  metal. 

6.  The  workman  is  in  no  danger  of  injuring  his  eyes  by 
excessive  light,  nor  is  the  current  at  all  dangerous.     The  operator 
works  without  dark  glasses  or  protective  apron  and  can  hold  the 
metal  bars  while  the  welding  is  going  on. 

The  present  limitations  of  the  process  seem  to  be: 

1.  Though   it  will  weld  odd   or  job  work,  it  is  practically 
limited  to  continuous  welding  of  one  article,  known  as  repeat 
welding. 

2.  Though  such  metals  as  brass  and  cast  iron  can  be  welded- 
on  the  Thomson  machine,  the  company  does  not  -  recommend 
it  for  such  metals  as  have  a.  marked  melting  point  and  which 
are  not  plastic  below  that  point.     High-carbon  steel  does  not 
give  an  altogether  satisfactory  weld  with  this  process. 

3.  The    machine    demands    power    at    irregular    intervals. 
For  this  reason  station  engineers  may  object  to  having  a  single 
machine  of  large  size  on  their  lines. 

Apparatus  and  Current. — The  Generator. — Welding  work 
can  be  done  with  current  from  city  lighting  circuit  or  the  firms 
will  sell  a  generator  built  for  the  purpose.  A  machine  built 
for  sizes  of  iron  and  steel  not  more  than  1/3  inch  square  may 
be  connected  to  the  city  alternating  lighting  wires  at  54  or  104 
volts,  requiring  no  transformer.  For  work  larger  than  1/3  inch 
square  section  it  is  best  to  get  the  alternating  generator  made 


44 


WELDING 


for  the  machine.     The  following  is  a  table  of  dynamos  especially 
adapted  to  welding: 

Generators  Specially  Adapted  for  Electric  Welding,  220  to  3300  Volts 
(Warren  Electric  Mfg.  Co.) 


K.  W. 

R.P.  M. 

Approx. 

Price 

K.  W. 

Exciter 

Standard  Pulley 

Weight 

list 

exciter 

R.  P.  M. 

D.      F. 

22.5 

900 

3100 

1250.00 

i 

1725 

2li 

4i 

30 

1  200 

3200 

1300.00 

i 

J725 

16 

4i 

50 

900 

4900 

1700.00 

i 

1725 

21* 

7i 

60 

900 

6500 

1850.00 

li 

1600 

«i 

1C 

60 

720 

8200 

2200.90 

ii 

1600 

27 

9i 

60 

600 

9100 

2550.00 

rl 

1600 

32 

?| 

75 

720 

9400 

2550.00 

2 

i45° 

27 

"i 

75 

600 

10500 

2800.00 

2 

i45° 

32 

I2i 

90 

720 

10800 

2800.00 

2 

145° 

27 

15 

100 

600 

12000 

3200.00 

2 

i45° 

32 

15 

In  this  process  alternating  current  is  invariably  used,  though 
there  is  no  electrical  reason  why  direct  current  should  not  be  used. 
It  is  claimed  for  alternating  current  that  its  heating  action  is 
more  uniform.  As  it  flows  mostly  on  the  surface  of  the  conductor, 
its  heating  effect  begins  and  is  most  intense  on  the  surface.  This 
heat  is  evenly  conducted  to  the  core  of  the  welded  pieces;  thus 
the  radiation  and  conductance  are  offset.  The  periodicity  of 
the  current  may  vary  between  50  and  250.  As  low  as  20  may  be 
used.  Guarini1  recommends  80  to  250  on  welds  of  4-inch  square 
section,  which,  however,  is  larger  than  work  ordinarily  welded  by 
electricity.  The  lower  the  periodicity,  the  less  will  be  the  skin 
effect,  and  hence  the  less  the  tendency  for  the  current  to  crowd 
toward  the  outside  of  the  parts  to  be  welded.  The  Thomson 
machine  is  now  designed  for  alternating  current  of  40  to  60  cycles. 

Figure  15  shows  the  Thomson  apparatus  diagramatically. 

The  Transformer. — Current  from  a  lighting  circuit  of  54  or 
104  volts  can  be  carried  directly  to  the  welding  clamps  without 

1  Scientific  American  Supplement,  Nov.  5,  1904. 


THE   THOMSON   PROCESS  45 

being  transformed.  Such  a  welder  is  called  a  direct  welder,  and 
is  used  for  small  work  only.  With  current  of  a  220-  or  440- volt 
circuit  a  transformer  is  necessary.  Besides  which,  it  is  safest 
and  cheapest  to  use  a  current  of  not  more  than  4  to  10  volts  in 
any  event. 

The  transformer  used  is  of  the  core  type.  It  consists  of  a 
core  of  soft  iron  surrounded  with  the  primary  and  secondary 
coils,  the  first  of  which  introduces  the  primary  current  at  rela- 
tively high  voltage  and  low  amperage,  and  the  second  of  which 
leads  off  the  current  for  the  secondary  or  welding  circuit  at 


FIG.  15. — Diagram  of  Thomson  electric  welder. 

relatively  low  voltage  and  high  amperage.  The  secondary 
coil  is  a  solid  copper  casting  encircling  the  core.  In  the  larger 
machines,  the  heating  effect  of  the  current  transformation  is 
overcome  by  passing  a  steady  current  of  oil  over  the  transformer 
which  is  encased  in  a  tight  box.  This  oil  is  either  air-  or  water- 
cooled. 

Figure  16  shows  a  machine  with  two  transformers,  one  for 
heating  and  one  for  welding.  The  machine  is  described  as 
follows: 

"  There  are  two  separate  transformers  in  the  machine,  on 
one  of  which  is  mounted  a  gun-metal  platen,  sliding  on  the  right- 
hand  or  welding  transformer.  The  left-hand  contact,  or  elec- 
trode, is  located  between  the  contacts  of  the  heating  transformer 
and  is  adjustable  for  any  required  space  between  the  electrodes 
of  the  two  transformers  by  a  screw  at  the  left  of  the  welder;  the 
right-hand  platen  being  moved  to  and  from  the  left-hand  contact 
by  the  pressure  lever  at  the  right.  The  cam  levers,  which  hold 
the  piece  to  be  welded  tightly  on  the  electrodes,  are  fastened  to 


40  WELDING 

the  cast-iron  bracket,  and  are  adjustable  to  varying  thicknesses 
of  stock. 

"The  circuit  in  the  transformers  is  opened  and  closed  by  two 
pole  break-switches,  which  are  furnished  with  the  welder  and 
should  preferably  be  installed  at  the  back  of  the  machine;  treadles, 
which  are  connected  by  chains  to  the  break-switches,  project 
under  and  at  the  front  of  the  welder,  and  are  operated  by  foot. 

"  One  piece  is  laid  on  the  terminals  of  the  heating  transformer 
in  the  direction  of  front  to  back  of  the  welder,  and  is  securely 


FIG.  16. — Thomson  double  transformer  electric  welder,  for  dash  and  fender 
frames.  The  clamping  device  can  be  modified  to  take  other  right-angle  and 
of  welds. 

held  by  bringing  forward  the  cam  lever,  the  circuit  is  then  closed 
by  placing  the  left  foot  on  the  break-switch  lever,  and,  while  the 
piece  is  rapidly  heating  between  the  electrodes,  the  other  piece 
is  laid  on  the  electrodes  of  the  right-hand  or  welding  transformer 
and  tightly  clamped  by  the  other  cam  lever.  The  foot  is  then 
released  from  the  break-switch  treadle  of  the  heating  transformer 
and  transferred  to  that  of  the  -welding  transformer,  when  the 
second  piece,  immediately  coming  to  a  welding  heat,  is  forced 


THE    THOMSON   PROCESS 


47 


against  the  heated  section  of  the  first  piece  by  the  pressure  lever, 
upsetting  against  and  fusing  with  it.  The  foot  is  then  removed 
from  the  break-switch  treadle,  and  the  cam  levers  are  thrown  back, 
releasing  the  welded  pieces." 

The  transformer  is  the  heaviest  part  of  the  welding  machine. 
So  it  is  placed  in  the  body  of  the  welder  frame,  underneath  the 
clamping  table.  It  thus  gives  stability  to  the  machine.  Figure 
1 6  shows  the  transformers  in  plain  sight.  In  figure  21  the 
transformer  is  covered  from  view  in  the  body. 

Typical  Thomson  Welders 


Floor  space 

Maximum  area  Q" 

Weight  in 

Maximum 

H.  P.  to 

pounds 

Length 

Width 

watts 

Iron 

Copper 

dynamo 

T2  C 

f/ 

12" 

T  non 

2 

IS" 

12"                    2,OCO 

.10 

4 

IdO 

IT,"                  T/I"                  <?  non 

.0200 

A 

525 

4" 

15"             5»oo° 

•30 

.110 

9 

800 

28" 

18" 

7,000 

•25 

12 

900 

32"                    20"                 10,000 

.60 

.20 

17 

2,200 

54" 

3o" 

2O.OOO 

1.23 

.40 

35 

2,400 

70"                   30"                 20,000 

1.23 

.40 

35 

7,OOO                      90''                   36"                 4O,OOO 

3- 

•79 

80 

Regulating  Apparatus. — Regulating  apparatus  includes  a 
switch-board  on  which  are  assembled  a  reactive  coil,  rheostat, 
potential  indicator,  and  fuse  blocks  and  switches;  and  apparatus 
for  automatically  shutting  off  the  current  of  the  primary  when 
welding  heat  is  reached. 

The  reactive  coil  (Fig.  17)  is  to  control  the  current  at  the 
welder  when  a  great  variety  of  sizes  is  to  be  welded.  It  consists 
of  an  iron  base,  a  copper  hood,  a  switch,  and  two  laminated  iron 
cores;  the  smaller  core  carries  the  copper  hood  and  partly  rotates 
within  the  larger  core  which  has  four  distinct  coils  wound  on  it. 
These  coils  can  be  connected  either  in  series,  series  multiple, 
or  multiple,  by  means  of  the  switch  in  the  base,  which  is  operated 
by  the  handle  projecting  through  side  of  base.  The  hood  is 
moved  over  the  winding  by  a  worm  gear,  which  is  operated  by 
the  wheel  at  the  front. 


WELDING 


When  the  switch  handle  is  in  position  No.  i  and  the  hood 
farthest  away  from  the  winding,  the  minimum  current  is  obtained. 
When  the  switch  handle  is  in  position  No.  2  and  the  hood 
farthest  away  from  the  winding,  the  mean  current  is  obtained. 

When  the  switch  handle  is  in  position  No.  3  and  the  hood 
over  the  winding,  the  maximum  current  is  obtained. 

The  reactive  coil  also  regulates  the  potential  for  metals  like 

iron,  which  are  good  con- 
ductors when  cold  and  be- 
come more  resistant  when 
hot. 

A  fairly  efficient  make- 
shift rheostat  was  formerly 
made  of  a  barrel  of  water 
into  which  a  metal  disk  was 
lowered  and  raised.  The 
disk  served  as  one  pole  and 
the  bottom  of  the  barrel  as 
the  other  pole.  The  sides 
of  the  barrel  were  insulated. 
Regarding  the  high  peak 
loads  caused  by  a  large 
Thomson  machine,  The  Elec- 
trical Times1  has  this  to  say : 
"Central  station  engineers  have  hitherto  been  somewhat 
chary  in  connecting  electric  welders  of  large  size  to  their  mains 
on  account  of  the  fluctuating  nature  of  the  load,  although  there 
are  numerous  instances  of  small  welders  being  so  used.  A  very 
interesting  installation  has  recently  been  completed  in  London 
by  the  Electric  Welding  Company,  Limited,  in  which  a  welder 
of  90  k.w.  capacity  is  worked  off  a  single-phase  power  supply 
at  400  volts.  In  order  to  prevent  undue  fluctuations  of  voltage 
on  the  mains,  a  special  substitutional  resistance  is  installed,  built 
in  three  sections,  each  controlled  by  a  switch,  so  that  one  or  more 
sections  can  be  put  in  circuit  according  to  the  size  of  the  work 
being  welded.  A  large  liquid  resistance  is  also  employed  to 
prevent  an  undue  rush  of  current,  when  the  primary  circuit 

September  5,  1907. 


FIG.  17. — Thomson  type  reactive  coil,  for 
controlling  current  in  welding  machine. 


THE    THOMSON    PROCESS 


49 


of  the  welding  transformer  is  closed,  the  plates  being  raised  and 
lowered  by  a  small  motor  through  suitable  gearing.  The  con- 
trolling switch  of  the  welder  is  so  arranged  that  when  put  in  the 
'on'  position  it  starts  the  plate-lowering  gear,  thus  gradually 
cutting  out  the  starting  resistance,  and  vice  versa.  This  plant 
is  in  continuous  operation,  and  no  inconvenience  to  other  power 
users  in  the  neighborhood  has  been  reported.  Another  welder 
of  smaller  size  has  also  been  connected  to  this  circuit.  '  In  this 
case  a  special  economy  coil  is  used  as  a  regulating  device. 

"To  facilitate  the  working  of  electric  welding  machines  on 
polyphase  circuits,  Professor  Elihu  Thomson  has  recently  pat- 
ented a  method  of  winding  the  trans- 
formers to  prevent  unbalancing  the 
phases.  This  will  doubtless  lead  to 
considerable  development  in  the  near 
future,  seeing  that  the  power  com- 


A  B 

FIG.  18. — Two  types  of  Thomson  automatic  break  switches. 

panics'  supply  mains  are  available  in  most  manufacturing 
centres." 

On  account  of  the  type  of  welds  it  handles,  the  Thomson 
welder  is  often  made  automatic.  Suppose  a  welder  is  being 
fed  links  of  a  chain  to  be  welded.  If  the  welder  will  put  through 
each  weld  automatically,  a  uniform  product  will  be  secured  and 
labor,  time,  and  current  will  be  saved.  The  automatic  shut-off 
(Fig.  18,  a)  is  a  switch  in  the  primary  circuit  which  is  thrown 
open  as  soon  as  the  clamps  move  together  on  the  yielding  metal. 
The  current  is  not  used  any  longer  than  is  necessary  to  heat  the  joint. 

The  break-switch  shown  in  figure  18,  a  is  used  with  the  larger 
welders,  heavy  currents  being  employed,  and  should  be  installed 
4 


50  WELDING 

at  the  back  of  the  welder.  The  switch  is  out  of  reach  and  is 
operated  with  the  foot  by  the  lever;  this  lever  should  run  under 
the  base  of  the  welder,  the  end  projecting  at  the  front  of  the 
welder  at  a  convenient  place  for  the  operator. 

The  break-switch  shown  in  figure  18,  b  is  used  with  the  smaller 
welders  for  wire  and  thin  flat  sections,  etc.,  when  the  weld  is 
made  instantaneously  and  should  be  installed  at  a  convenient 
height  against  the  left  of  the  welder.  The  switch  is  operated  by 
hand,  the  lever  being  pressed  down  on  to  the  shoulder  at  the  front, 


FIG.  19. — Thomson  universal  welder  with  horizontal  oblique  clamping  device  and 
hydraulic  jack  for  pipe  straight-away  and  miscellaneous  work. 

where  it  locks,  being  automatically  released  when  the  weld  is 
made,  by  a  cut-out  device  on  the  welder,  a  spring  throwing  up 
the  lever. 

When  the  piece  to  be  welded  does  not  heat  evenly,  the  lever 
should  be  lightly  and  intermittently  pressed  against  the  shoulder 
without  locking,  until  the  heat  is  evenly  distributed,  when  it 
should  be  locked,  as  before  stated. 

The  Clamps. — The  clamps  vary  in  design  in  different  types 
of  machines.  Figures  16  and  19  show  clamps  for  various  work. 
They  are  generally  of  heavy  copper,  to  allow  for  the  passage  of  the 
large  volume  of  current.  The  clamps  are  not  rigid  in  a  welding 


THE    THOMSON   PROCESS  51 

machine,  but  are  pivoted  or  mounted  on  a  straight  sliding  groove, 
and  are  made  to  move  toward  each  other  by  a  lever,  wheel-and- 
screw,  or  by  hydraulic  pressure.  Recently  the  hydraulic  pressure 
has  been  made  automatic,  so  that  the  machine  will  throw  on  its 
own  current  as  soon  as  the  pieces  to  be  welded  are  clamped,  will 


FIG.  20.— Thomson  special  machine  for  welding  hubs  and  spokes  in  agricultural 
wheels.     Approximate  weight  7,500  pounds. 

squeeze  the  pieces  together  at  the  temperature  of  plasticity,  and 
will  throw  off  the  current  at  the  same  time. 

Where  heavy  bars  are  to  be  welded,  and  a  good  electri- 
cal contact  is  needed  at  the  clamps,  the  clamps  are  operated 
hydraulically. 

As  will  be  guessed,  the  clamps  are  liable  to  get  very  hot, 


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54 


WELDING 


especially  on  continuous  runs  of  heavy  work.     As  heat  affects  the 
conductivity  of  the  clamps,  they  are  often  water-cooled. 

Some  of  the  automatic  machines  are  equipped  with  swages 
working  between  the  electrodes.  These  swages  are  brought 
together  on  the  weld  immediately  after  the  hot  metal  is  upset. 
They  compress  the  upset  or  bur  and  give  the  weld  any  desired 
shape.  Besides  which,  their  pressure  amounts  to  working  of  the 
metal  and  makes  the  weld  much  stronger. 


FIG.  21. — Thomson  type  5  AA  electric  welder  for  copper  wire  from  No.  6  to 
1-4  inch.  Time  in  heating  from  2  to  6  seconds.  7500  Watt  alternating  current, 
not  lower  than  50  cycles,  from  100  to  350  volts. 

Practice. — The  operation  of  the  Thomson  electric  welder 
is  very  simple,  calling  for  much  less  skill  than  the  hot-flame 
processes.  For  stock  welds  the  current  is  first  calculated  for  the 
size  of  the  piece  to  be  welded  and  the  kind  of  metal  in  the  piece. 
Tables  of  current  value,  cross-section,  and  time  have  been  worked 
out  for  iron,  steel,  brass,  and  copper  (see  page  52).  The  machine 
being  adjusted  for  stock  welds  will  handle  them  rapidly  without 


THE    THOMSON    PROCESS 


55 


readjustment,  much  the  same  as  a  printing  press  will  run  off 
many  impressions  of  the  same  form. 

The  operator  places  his  pieces  in  the  clamps,  closes  the  clamps, 
and  advances  the  clamps  toward  each  other  until  the  two  pieces 
touch  closely.  He  turns  on  the  current  and  as  soon  as  the  pieces, 
become  plastic  or  semi-molten  at  the  point  of  contact  he  turns 
off  the  current  and  squeezes  the  clamps  toward  each  other  until 
the  pieces  become  welded  and  upset  at  the  contact. 

Figure  21  shows  a  semi-automatic  machine.  The  copper 
contacts,  carrying  the  clamping  device,  move  to  and  from  each 
other:  the  left  is  moved  by  a  screw  to  get  the  required  opening  be- 
tween clamps;  the  right  is  held  apart  by  the  lever.  The  wire  is 
inserted  and  tightly  held  in  the  clamps,  the  side  lever  raised,  the 
circuit  closed  through  the  hand-automatic  break-switch  in  the 
base  of  the  welder,  and  the  pieces,  instantly  heating  at  the  joint, 
are  forced  together  by  the  weights;  the  circuit  being  automatically 
opened  by  the  adjustable  cut-out  device. 

In  making  the  joint,  the  metal  is  upset,  the  extent  of  which 
depends  largely  upon  the  weights  and  the  adjustment  of  the  cut- 
out device. 

When  full  range  of  sizes  is  to  be  welded  or  when  the  smaller 
sizes  only  are  to  be  welded,  a  current  controller  is  furnished  with 
the  welder. 

Energy  Absorbed  in  Electric  Welding— Prof.  Thomson's  Process 


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WELDING 
Iron  and  Copper 


Sp.  heat 

Cond. 

Melting  point, 
deg.  Cent. 

Arcing  volts 

Iron  

o.  113 

•274 

i6"K 

2$ 

CoDDer.  .  . 

O.OCK 

808 

1080 

23 

Copper  requires  two  or  three  times  as  much  power  and  only 
0.6  time  as  long  time  as  iron.  Rectangular  pieces  require 
25  to  50  per  cent,  more  power  than  circular.  A  machine  that 
will  weld  2-inch  iron  will  take  i  i/4-rnch  brass  and  7/8-inch 
copper. 

As  is  seen  by  the  tables,  the  actual  time  of  welding  after  the 
current  is  turned  on  is  often  less  than  one  minute  per  weld;  the 
advantage  of  quick  handling,  automatic  clamping,  and  automatic 
current  shut-off  are  very  apparent.  With  skilled  labor  and 
automatic  machines,  many  firms  are  new  turning  out  from  500 
to  3000  welds  per  machine  per  ten-hour  day. 

For  job  work  the  welder  is  slower  and  a  skilled  man  should 
be  the  operator.  If  he  is  called  on  to  weld  a  succession  of  dif- 
ferent sizes,  shapes,  and  different  metals  he  will  have  to  use  his 
gray  matter  continually  in  the  regulation  of  the  current,  clamps, 
and  the  amount  of  uspet  and  time  of  cooling  before  removal 
from  the  clamps.  Many  firms  use  this  welder  for  job  welding, 
though  it  is  not  specially  adapted  to  job  work. 

A  number  of  precautions  are  necessary  in  the  different  steps 
of  welding.  In  the  first  place,  the  metal  should  be  very  clean, 
both  at  the  clamps  and  at  the  points  of  contact  where  the  weld 
is  to  be  made.  The  metal  can  be  cleaned  in  a  number  of  ways. 
If  the  metal  pieces  are  at  all  oily  they  are  first  dipped  in  a  bucket 
of  lye  and  then  in  a  bucket  of  water.  If  the  pieces  have  any 
petroleum  oil  on  them,  the  lye  will  not  clean  them,  and  they  must 
first  be  wiped  down  with  waste.  Sand-blasting  and  tapping 
will  remove  the  scale.  Any  remaining  dirt  can  be  forced  out 
into  the  upset. 


THE    THOMSON   PROCESS 


57 


Then  the  clamps  must  be  set  lightly  on  the  pieces,  and  the 
contact  surfaces  must  be  as  large  as  possible  so  that  there  will  be 
good  electric  conductance.  If  the  contact  at  the  clamps  is  im- 
perfect the  clamps  will  become  heated. 

The  distance  between  the  clamps  varies  with  the  diameter  of 
the  metal  pieces  and  also  with  the  kind  of  metal.  In  a  general 
way,  the  distance  between  clamps  is  equal  to  twice  the  diameter, 
with  iron;  is  three  times  as  great  as  the  diameter,  with  brass;  and 
four  times,  with  copper.  This  difference,  of  course,  is  caused  by 
the  higher  conductivity  of  copper,  which  requires  the  immense 
volume  of  60,000  amperes  per  square  inch  of  metal. 


80 


40 


20 


jet 


1234 

Area  in  Sq.  in* 

FIG.  22. — Power  and  time  required  to  weld  iron  (Standard  Handbook  for  Electrical 

Engineers). 

Some  metals  are  best  heated  rapidly.  Steel,  rolled  copper, 
and  like  metals,  which  are  easily  ruined  by  heat,  must  be  handled 
with  care.  They  must  be  heated  as  quickly  as  possible;  and 
they  must  not  be  overheated,  or  they  will  lose  their  structure. 
The  act  of  forcing  the  hot  ends  together  and  squeezing  the  metal 
helps  to  maintain  the  structure  and  prevent  crystallization. 
Such  metals  should  be  worked  or  hammered  while  cooling.  In 
welding  tool  steel  the  ends  are  forced  together  until  the  over- 
heated metal  is  all  forced  out  of  the  joint  into  the  upset.  Of 
course,  any  scale  or  dirt  is  also  forced  out.  When  copper  wire 
is  welded,  it  should  be  upset  and  then  drawn  down  to  the  proper 
gauge.  In  this  way  joints  of  nearly  equal  strength  can  be 


50  WELDING 

made.  While  quick  heating  is  a  good  thing,  the  joint  can  easily 
be  heated  so  rapidly  that  it  will  be  overheated.  No  metal  can 
stand  overheating. 

Contrary  to  common  conception,  the  welding  heat  is  not  caused 
by  imperfect  contact  at  the  joint.  The  pieces  should  fit  as  closely 
as  possible  before  welding.  A  poor  contact  will  simply  delay  the 
heating. 

Rapid  welding  calls  for  larger  dynamo  and  welder  at  greater 
cost,  but  the  increased  efficiency  will  more  than  pay  for  the  outlay. 


60 


50 


40 


80 


20 


10 


0.2  0.4  0.6 

Area  in  Sq.  in. 

FIG.  23. — Power  and  time  required  to  weld  copper  (Standard  Handbook  for  Elec- 
trical Engineers). 

Seven-horsepower  minutes  is  given  as  the  approximate  figure  for 
bringing  one  cubic  inch  of  iron  to  welding  heat.1  If  the  metal 
clamps  conduct  the  heat  away  rapidly,  from  10-  to  15-horsepower 
minutes  are  required. 

All  of  the  metals  of  commerce  have  been  welded  by  this  process, 
both  to  themselves  and  to  each  other.  Those  metals  which  are 
most  plastic  at  welding  heat  and  which  have  the  widest  range  of 
plasticity  will  weld  the  most  readily.  Metals  which  oxidize  can 
be  fluxed  with  borax,  sand,  sal  ammoniac,  zinc  chlorid,  etc.,  but 

1  The  Engineering  Magazine,  Hermann  Lemp,  Aug.,  1894. 


THE    THOMSON  PROCESS  59 

in  most  cases  fluxing  is  not  necessary.  The  oxid  at  the  contact 
can  be  forced  out  into  the  upset.  Brass  is  generally  fluxed. 

Prof.  Thomson  has  in  his  possession  a  metal  bar  of  3/8-inch 
diameter  which  is  made  of  nine  different  metals  welded  together. 
However,  the  Thomson  Company  does  not  recommend  its 
machine  for  cast  iron  or  similar  metals  of  well-defined  melting 
point  and  which  are  brittle  up  to  that  melting  point.  Cast-iron 
pieces  can  be  melted  in  the  welder  and  their  ends  stuck  together. 
It  is  necessary  to  build  up  a  clay  or  asbestos  form  around  the 
joint  so  that  the  metal  will  not  run  away  when  it  melts.  Brass 
must  be  treated  in  the  same  way.  On  cooling  it  will  become 
brittle  and  crystalline.  This  is  a  trouble,  however,  which  is  com- 
mon to  all  the  welding  processes.  If  you  are  welding  a  trouble- 
some metal  you  may  as  well  expect  doubtful  results.  The  weld- 
ing of  copper  by  this  process  has  been  a  disappointment  to  some, 
while  others  claim  complete  success  for  their  copper  welds.  It  is 
evident  that  the  difference  between  good  and  bad  welds  in  many 
instances  is  due  to  the  skill  employed. 

Adaptability. — In  the  last  decade  the  Thomson  or  similar 
machines  have  forced  their  way  into  many  of  the  metal  trades. 
In  factories  where  stock  welds  are  made,  this  process  is  invalu- 
able. There  is  a  long  list  of  implements  that  are  now  welded  in 
the  process  of  making.  Those  industries  which  are  most  bene- 
fited are  the  wagon  and  carriage,  bicycle,  tools,  wire,  chain,  pipe 
and  pipe  bending,  and  miscellaneous,  which  includes  angle 
welding,  typewriters,  printers'  chases,  wire  fence,  tool  steel  to 
steel,  springs,  bands  and  rings,  umbrella  rods,  etc. 

Occasionally  the  joining  of  two  different  kinds  of  metals  or  of 
metals  of  unequal  sizes  will  call  forth  the  ingenuity  of  the  work- 
man. Copper  and  brass  are  frequently  welded  to  iron.  When 
metals  of  unequal  electrical  conductivity  are  welded,  the  clamps 
are  placed  according  to  the  conductivity  of  the  metal.  Thus, 
for  copper  on  iron,  the  iron  clamp  would  be  placed  one  diameter 
away  from  the  end  of  the  iron,  and  the  copper  clamp  three  times 
the  diameter  away  from  the  end  of  the  copper  piece.  Copper  and 
iron  weld  fairly  well  because  their  melting  points  are  fairly  close 
and  they  will  alloy  at  the  contact.  On  account  of  the  great  dif- 
ference in  conductivity,  however,  the  iron  will  become  much 


6o 


WELDING 


hotter  than  the  copper  piece,  unless  the  latter  is  pointed  or  whittled 
down  as  shown  in  figure  24. 

Another  problem  has  been  to  join  a  bar  of  iron  to  an  iron  plate. 
In  this  case,  the  current,  under  ordinary  conditions,  would  flow 
off  of  the  surface  of  the  bar  on  account  of  the  larger  area  of  the 
plate.  The  bar  would  become  heated  only  on  the  periphery  of 

the  end,  and  the  plate  would 
not  be  heated  to  redness.  To 
prevent  the  current  from 
spreading  at  the  junction,  a 
circular  channel  is  cut  into 
the  plate  at  the  proposed 


Clamps  Clamps 

~j  2  Diameters 


Iron 


Copper 


Diameterl 


FIG.  24. — Welding  iron  to  copper. 
Showing  adjustment  of  clamps  and  shape 
of  copper. 


junction,  as  shown  in  figure 
25.  In  a  similar  way  a  large  bar  can  be  butted  on  to  a  smaller 
bar  by  cutting  or  whittling  the  end  of  the  large  bar. 

Wire  factories  can  butt-weld  their  wire  ends,  thus  saving  waste 
pieces  and  allowing  them  to  make  any  length  of  wire  specified. 

The  carriage  and  bicycle  trades  have  been  much  benefited 
by  the  Thomson  process.  Frames,  hubs,  spokes,  steps,  etc.,  are 
welded  by  this  process.  In  bicycle  manufacture,  tubes,  forks, 
pedals,  crank  hangers,  mud-guards,  etc.,  are  welded.  Automo- 
bile making  is  equally  dependent  on  electric  welding. 


Channel 


FIG.  25. — Showing  how  a  bar  is  welded  to  a  plate. 

Iron  or  brass  pipe  is  butt-welded  and  also  heated  prepara- 
tory to  bending.  In  England  wrought-iron  pipes  are  flanged 
very  successfully. 

A  number  of  firms  weld  printers'  chases  by  this  method.  The 
bars  are  held  in  the  hands  of  the  operator,  are  butt-welded,  and 


THE    THOMSON   PROCESS 


6l 


then  right-angled  on  a  frame.     The  burr  or  upset  is  trimmed  off 
on  a  metal  saw  and  ground  even  on  a  wheel. 

Chain  is  being  welded  by  the  electrical  process;  as  fast  as  two 
links  a  minute  can  be  turned  out  on  the  smallest  sizes.  In  this 
case  some  of  the  current,  approximately  10  to  30  per  cent.,1  travels 
around  the  ring  instead  of  over  the  joint.  This  loss  of  current 
is  expensive  and  stands  in  the  way  of  the  general  adoption  of  this 


FIG.  26. — Thomson  specimens.     Type  bars,  steel  to  brass;  angle  weld;  bicycle 
rk;  hoe;  corner  angle  weld;  chain,  two  welds;  chain  showing  fin  after  welding; 

.     •__ 11 i i   r  -   i 


fork, 

chain  welded  and  fin  removed. 


process  to  chain  welding.  But  it  is  also  claimed  that  this  short- 
circuiting  of  part  of  the  current  causes  the  ring  to  heat  suffi- 
ciently to  bend  with  ease  when  the  ends  of  the  link  are  closed. 
It  is  claimed  that  a  bar  magnet  thrust  through  the  link  to  be 
welded  will  largely  prevent  the  current  from  traveling  around  the 
link. 

In  the  welding  of  hoops  and  rings  this  same  objection  appears. 
The  loss  of  current  is  much  less  for  rings  of  large  diameter  and 

1  Iron  Age,  W.  S.  Gorton,  July  27,  1905. 


62 


WELDING 


small  gauge,  and  can  be  further  reduced  by  placing  the  clamps 
closer  than  is  the  custom. 

Electric  welding  is  much  used  in  the  manufacture  of  projec- 
tiles and  the  parts  of  machine  guns.  A  special  high-carbon  head 
can  be  welded  on  to  a  soft-steel  projectile  cartridge. 

Brass  heads  are  joined  to  steel  shanks  for  use  in  switchboards. 

Garden  rakes  that  were  once  made  of  cast  iron  are  now  made 


FIG.  27. — Thomson  specimens.  Tee  weld  in  pipe;  furrule;  wire  handles; 
bicycle  head;  sheaves;  band  saw  steel  automobile  rim;  pipe;  tee  weld;  wire  mesh. 

much  lighter  and  stronger  by  putting  the  teeth  on  a  bar.  Both 
teeth  and  bar  are  of  wrought  iron  or  steel,  and  are  lighter  and 
much  stronger  than  the  old  cast  rake. 

Wheelbarrows  are  made  of  welded-steel  wheels  and  frames. 
In  the  wheels,  the  rim  is  welded  into  a  hoop,  and  the  spokes  are 
welded  both  to  the  rim  and  to  the  hub. 

The  heads  of  cap  screws  are  now  successfully  welded  onto  the 
shanks.  This  allows  the  manufacturer  to  cut  his  thread  in  the 


THE    THOMSON   PROCESS 


hard  outer  layer  of  steel.  Formerly  the  screw  was  cut  from  a 
billet  of  the  diameter  of  the  head.  The  head  was  harder  than 
the  thread  which  was  turned  out  of  the  softer  metal  near  the 
core.  It  is  claimed  that  the  increased  strength  of  the  thread 
and  the  decreased  cost  of  turning  down  the  shank  offset  the  cost 
of  welding. 


FIG.   28. — Thomson  specimens.     Printer's  chase;  carriage  rail;  bag  frame  flat; 
T  weld;  bag  frame  on  edge;  dash  frame. 

Rail  welding  was  first  suggested  by  Thomson  and  practised 
with  one  of  his  machines.  On  account  of  the  importance  of  elec- 
tric rail  welding  and  the  special  apparatus  needed,  the  process 
will  be  described  in  detail. 

The  most  recent  application  of  the  Thomson  process  is  to  the 
welding  of  sheets  of  metal.  Two  sheets  of  steel  are  lapped 


64 


WELDING 


and  welded  at  regular  intervals  in  points  similar  to  riveting. 
"The  method  consists  in  bringing  two  pointed  electrodes  against 
the  two  sheets,  or  prepared  sheets  with  slight  projections,  by 
indenting  or  punching.  The  current  flows  through  these  projec- 
tions which  are  pressed  down  flat  on  the  sheet,  effecting  the  weld. 
This  method  is  used  in  interior  furnishings  of  steel  railway  cars, 
passenger  coaches,  steel  furniture,  sheet-metal  ware,  etc."1 


FIG.  29. — Thomson  specimen.     Automobile  clincher  rim. 

Locomotive  Flue  Welder. — The  Warren  Electric  Manu- 
facturing Company  has  furnished  the  following  description  of 
their  flue  welder,  which  is  especially  adapted  to  the  work : 

"The  flue  welder  (Fig.  30)  operates  from  an  alternating  source 
of  electromotive  force,  and  steps  the  voltage  from  any  convenient 
line  voltage  down  to  from  5  to  16  volts  on  the  weld  by  means  of  a 
transformer  enclosed  in  the  body  of  the  welder.  The  secondary 
leads  from  the  transformer  are  connected  to  two  copper  contact 
shoes,  which  hold  the  ends  of  the  flues  to  be  welded.  These 
contact  shoes  have  a  copper  top  clamping  piece,  operated  by  cam 
levers,  which  clamp  the  flue  very  securely.  The  top  and  bottom 
members  of  this  clamp  are  cooled  by  means  of  running  water. 
One  of  these  pipe  clamps  which  holds  the  shorter  end  of  the  flue 
is  operated  longitudinally  by  means  of  a  lever,  so  as  to  bring  the 
ends  of  the  flues  into  contact  under  heavy  pressure.  One  of  the 
foot  treadles  operates  a  switch  in  the  primary  circuit  for  controll- 
ing the  heating  of  the  joint.  The  second  treadle  operates  a  die 

1  Special  information  furnished  by  the  company. 


THE    THOMSON   PROCESS 


which  is  brought  up  so  as  to  surround  the  joint  at  the  time  at 
which  compression  takes  place  and  prevent  an  external  upset 
around  the  pipe  at  the  joint.  This  die  is  also  water-cooled. 

"  Owing  to  the  circular  form  of  the  pipe,  the  compression  at 
the  joint  produces  a  pressure  on  the  interior  portion  of  the  pipe, 
which  increases  the  density  of  the  metal.  This  increased  density 
resists  the  tendency  to  expand  internally,  as  the  metal  naturally 


FIG.  30. — Locomotive  flue  welder. 

expands  in  the.  direction  of  the  least  resistance.  It  has  been  found 
experimentally  that  there  is  no  tendency  whatever  to  an  upset 
on  the  inside  of  the  pipe.  When  the  flues  are  welded  without 
the  clamp  die,  the  free  flow  of  the  metal  is  all  outward,  which 
produces  an  exterior  upset  only. 

"The  operation  of  the  welder  is  as  follows: 

"The  two  ends  of  the  flue  are  clamped  in  place,  and  then 
brought  into  contact  by  means  of  the  horizontal  hand  lever. 
The  current  is  thrown  on,  and  the  metal  at  the  joint  gradually 
5 


66 


WELDING 


brought  up  to  welding  heat.  Immediately  upon  reaching  the 
welding  heat,  the  current  is  thrown  off,  and  the  dies  for  controll- 
ing the  form  of  the  weld  are  brought  up  into  contact  with  the 
work  by  means  of  the  second  treadle.  A  further  movement  of 
the  horizontal  lever  is  then  made  so  as  to  produce  a  very  heavy 
compression  of  the  joint  inside  of  the  die.  After  compression 
the  die  is  then  released,  and  also  the  top  clamps,  so  as  to  relieve 
the  pipe  of  strains  during  the  cooling  of  the  joint. 

"The  advantage  of  this  form  of  welder  is  a  practically  smooth 
joint  on  the  outside  of  the  pipe,  which  permits  the  flues  after 
welding  to  be  placed  in  the  end  sheets  of  the  boiler  without 
reducing  the  upset  usually  met  with  on  butt-welds  made  by  the 
electrical  process.  In  welding  flues  electrically,  this  exterior 
upset  is  accompanied  by  an  expansion  of  the  pipe  at  the  joint, 
so  as  to  produce  an  annular  groove  inside  the  pipe,  which  is 
objectionable  in  boiler  flues  on  account  of  the  accumulation  of 
scale  therein.  This  annular  groove  is  of  course  entirely  elimi- 
nated in  the  flues  as  welded  by  this  machine." 

Rail  Welding  by  the  Thomson  Process. — The  most  im- 
portant single  application  of  the  Thomson  process  has  been  to  the 
welding  of  street-car  rails.  Before  1892,  all  rail  welding  was  done 
by  the  cast-welding  process.  Cast- welding  is  briefly  as  follows : 


Pressure  Bar 


Pressure  Block 


Mold 


FIG.  31. — Weld  and  pressure  block  in  place  for  cast  welding. 

It  is  desired  to  save  a  piece  of  track  from  scrapping,  that  is 
weak  at  the  joints,  and  whose  rail  heads  have  been  considerably 
worn.  The  cast-welder  machine  consists  of  two  cars.  The  first 
car  contains  the  sand  blast  which  cleans  all  dirt  from  the  rail  joint. 
A  cast-iron  mold  is  then  clamped  onto  the  joint,  and  the  ends  of 
the  rail  heads  are  pressed  down  by  a  block  which  prevents  them 
from  springing  when  the  joint  is  cast  (see  Fig.  31).  The  second 
car  is  now  moved  over  the  joint  mold.  This  second  car  contains 


THE    THOMSON    PROCESS  67 

the  melting  cupola— a  small,  coke-fed  blast  furnace  which  melts 
down  a  mixture  of  charcoal  iron  and  assorted  scrap  until  it  is  at  a 
high  temperature.  This  very  hot  iron  is  run  into  the  mold  and 
forms  a  cast-weld  around  the  heads  of  the  rails.  Examination 
of  this  joint  shows  that  the  cast  iron  of  the  joint  and  the  steel  of 
the  rail  have  amalgamated.  The  cast-weld  is  still  being  used, 
though  it  has  strong  opponents.  As  many  as  200  cast-welds  can 
be  made  per  day. 

In  Los  Angeles  there  are  several  hundred  miles  of  cast- 
welded  track  that  are  being  displaced  as  unsatisfactory.  Only 
one  joint  in  ten  was  found  to  have  amalgamated  at  the  so-called 
weld.  The  result  was  a  loss  of  electrical  conductivity  of  from 
25  to  75  per  cent.  The  cost  per  cast- welded  joint  was  given  as 
roughly  $7.00  as  against  $5.00  to  $6.00  for  the  thermit  joints 
which  are  displacing  them.  The  breakage  was  said  to  be  about 
two  per  cent  per  annum,  and  track  that  was  welded  in  cold 
weather  broke  the  least.  "Sun  snakes  "  were  a  common  occur- 
rence, and  were  prevented  by  building  the  paving  close  to  the 
rail.  No  open  rail  track  can  be  welded,  as  it  will  warp  and 
snake. 

Recently  the  electric  roads  have  begun  to  adopt  the  electrically 
welded  rail  and  also  the  thermit- welded  rail  (see  page  123). 
Welded  rails  are  a  great  improvement  over  those  joined  by  fish- 
plates and  bonded  with  copper  wire,  for  conducting  the  current: 

1.  The  conductivity  of  the  weld  is  as  good  or  better  than  the 
unit  section  of  rail.     There  is  no  bonding  to  come  loose  or  leak 
or  be  stolen. 

2.  The  rail  will  last  much  longer. 

3.  Welded  tracks  is  smoother  riding. 

Rails  running  through  city  streets  are  well  embedded  in  the 
street.  If  the  street  paving  is  not  a  good  conductor  of  heat  and 
the  extremes  of  summer  and  winter  temperature  are  not  too  great, 
very  long  sections  of  track  can  be  welded  into  one  piece  without 
fear  of  pulling  loose  at  the  ends  or  at  any  of  the  joints.  A  section 
of  2300  feet  has  been  solidly  joined  at  Holyoke,  Mass.  It  is  cal- 
culated that  the  coefficient  of  expansion  of  steel  in  such  a  climate 
would  cause  a  stress  of  about  16,000  pounds  to  the  inch,  while  the 
tensile  strength  of  the  rail  would  run  well  over  40,000  pounds. 


68 


WELDING 


Friction  of  the  pavement  against  the  rail  and  inertia  of  the  rail 
prevent  dragging,  and  the  expansion  and  contraction  are  taken 
up  by  the  elasticity  of  the  rail.  Rails  welded  with  thermit  or  by 
electricity  are  less  liable  to  crack  or  pull  apart  at  the  weld  than 
are  cast-welded  rails. 

The  Thomson  process  was  the  first  process  of  welding  applied 
to  the  production  of  continuous  rails  on  electric  railway  tracks, 

and   was   introduced   by  the 
Johnson  Company  in  1892. 

In  1897,  the  Lorain  Steel 
Company,  successors  to  the 
Johnson  Company,  improved 
the  process  and  placed  it  ac- 
tively on  the  market.  Since 
that  time  it  has  been  made  use 
of  in  almost  all  the  large  cities 
of  the  United  States,  and  the 
company  found  it  necessary  to 
double  its  equipment  for  this 
kind  of  work. 

The  joint  consists  of  two 
bars  welded  to  the  web  of  the 
rail,  one  on  each  side.  Three 
welds  are  made  between  the 
bars  and  the  rail,  one  directly 
over  the  ends  of  the  two  rails 
and  at  each  end  of  the  bars. 
The  central  weld  is  made  first. 


FIG.  32. — Thomson  special  machine  for 
welding  rails  in  streets. 


In  cooling,  the  contraction  of 
the  bars  draws  the  abutting 
rails  together  so  that  no  opening  remains  across  the  head  of 
the  rail. 

The  apparatus  is  mounted  on  four  trolley  cars,  propelled  by 
their  own  motors.  The  first  car  carries  a  sand-blast  apparatus 
for  cleaning  the  rails  and  bars.  The  welder  is  suspended  from  a 
crane  projecting  from  the  front  of  the  second  car  (see  Fig.  32). 
The  welder  itself  consists  of  a  "  step-down  transformer  for  supply- 
ing current  for  heating  the  weld,  and  hydraulic  pressure  apparatus 


THE    THOMSON   PROCESS  69 

for  supplying  a  heavy  pressure  to  the  portions  to  be  welded." 
Suitable  mechanism  is  carried  within  the  car  for  raising  and  lower- 
ing the  welder  and  to  swing  it  from  side  to  side  to  engage  either 
rail.  Coupled  to  the  welder  car,  the  third  car  carries  rotary 
transformer  and  regulating  apparatus  for  changing  the  direct 
current  from  the  trolley  to  alternating  current.  A  switchboard 
with  instruments,  etc.,  is  also  carried  in  this  car. 

The  fourth  car  carries  two  grinder  carriages,  one  suspended 
over  each  rail,  to  smooth  down  any  inequalities  that  may  exist  on 
the  head  of  the  rail  after  the  joint  has  been  welded  and  to  produce 
a  true  running  surface. 

The  process  has  been  successfully  applied  to  all  kinds  of  rail, 
both  girder  and  T-rails.  Also  to  the  welding  of  the  "third  "or 
conductor  rail  on  elevated  and  surface  lines. 

The  process  particularly  commends  itself  for  use  in  crowded 
city  streets  on  account  of  its  harmlessness,  as  it  is  not  affected  by 
dampness  and  there  is  no  danger  of  explosions,  etc.,  due  to  sud- 
den rain  storms.  The  apparatus  is  practically  noiseless  in  its 
operation. 

An  interesting  application  was  the  welding  of  the  T-rail  on 
the  surface  track  on  the  north  and  south  roadways  of  the  Brook- 
lyn Bridge  in  1906. 

The  cost  of  the  equipment  makes  it  more  desirable  for  a  rail- 
way company  to  have  the  welding  done  for  them  than  to  do  it 
themselves. 

The  apparatus  is  also  made  use  of  for  welding  heavy  copper 
cables  to  the  rails,  either  for  overhead  return  or  around  special 
work.  As  the  conductivity  of  the  welded  joint  is  greater  than  the 
rail,  a  most  perfect  system  of  bonding  is  thus  afforded  at  the  same 
time  with  the  elimination  of  the  joints. 

From  ten  to  twenty  welds  are  made  per  day  by  this  machine. 
The  breakage  is  said  to  run  less  than  5  per  cent.,  and  often  not 
higher  than  i  per  cent.  The  machines  are  leased,  not  sold,  and 
the  cost  must  accordingly  be  figured  on  the  rental,  power,  and 
labor  in  calculating  the  cost  per  joint. 

Electric  Resistance  Heater.— -Besides  its  use  as  a  welder, 
the  machine  may  be  used  as  a  preheater  of  metals  to  be  brazed 
or  bent.  It  will  sometimes  be  preferable  to  braze  or  solder  a 


7O  WELDING 

joint,  when  the  two  metals  cannot  be  allowed  to  lose  their  shape  or 
have  any  of  their  substance  pressed  into  an  upset:  the  welder 
can  then  be  used  as  a  preheater.  The  current  would  be  regu- 
lated to  bring  the  metals  to  a  slightly  lower-than-welding  heat 
and  keep  them  at  this  heat.  In  brazing  brass,  this  is  the  best- 
known  method  of  preheating,  because  a  torch  preheater  always 
burns  out  some  of  the  zinc  in  the  brass  and  oxidizes  the  copper. 

The  Thomson  welder  may  be  used  to  anneal  spots  in  armor 
plate.  This  is  done  by  connecting  the  positive  to  the  armor  plate 
and  pressing  the  negative  clamp  against  the  spot  to  be  annealed. 

Tests. — In  general,  tests  of  electric  welds  show  that  from 
75  to  95  per  cent,  of  the  original  strength  of  the  metal  is  reached. 
In  cases  where  the  upset  is  not  cut  off,  the  strength  can  be  in- 
creased above  100  per  cent.  Welds  of  low-carbon  steel  and 
low  sulphur-and-silicon  iron,  if  well  made  and  worked  or  drawn 
after  working,  will  approximate  100  per  cent,  in  strength. 

It  is  sometimes  asked  if  the  electric  current  does  not  damage 
the  metal.  Electric  welding  is  no  more  harmful  to  the  metal  than 
any  other  process.  In  fact,  the  control  of  the  heat  is  so  exact 
and  overheating  and  reheating  so  seldom  happen,  that  electric 
welds  run  uniformly  high  in  tensile  and  elastic  strength.  A 
"burned"  weld  seldom  occurs — the  oxid  at  the  joint  is  forced  out 
into  the  upset  and  ground  off.  It  may  be  emphatically  stated  that 
the  electric-resistance  welds  are  the  best  yet  made.  As  an  in- 
stance, such  a  misused  and  overstrained  utensil  as  a  printers' 
chase  seldom  gives  at  the  weld. 

Sir  Frederick  Bramwell1  states  that  i  i/8-inch  round  bars 
can  be  welded  in  2  1/4  minutes  with  an  average  tensile  strength 
of  91.9  per  cent.,  against  four  minutes'  time  and  89.8  per  cent, 
strength  when  smith-welded. 

The  results  of  a  series  of  tests  of  electrically  welded  metals 
carried  on  at  the  Watertown  Arsenal2  may  be  abridged  as  follows : 

Twenty-nine  broke  at  the  weld. 

Seventeen  within  2  inches  of  the  weld. 

Eleven  within  the  range  of  moderate  heat. 

Two  near  the  grips. 

"Elec.  Engineering  Formula,"  p.  673. 
2  Transactions  of  the  American  Society  of  Mechanical  Engineers,  1889,  p.  97. 


THE    THOMSON    PROCESS  71 

Welds  of  wrought  iron  were  5  to  10  per  cent,  below  unit 
strength;  fracture  fibrous  or  slightly  spongy. 

Welds  of  steel  were  from  50  to  80  per  cent,  less  than  unit 
strength. 

Copper  welded  at  5  to  10  per  cent,  less  than  unit  strength. 

Steel  welded  to  wrought  iron  at  about  the  strength  of  the  iron. 

Brass  gave  an  uncertain  weld  with  wrought  iron  and  had  a 
strength  at  the  weld  of  8  1/2  to  16  1/2  tons  to  the  inch. 

Steel  welded  with  German  silver  with  a  strength  of  20  tons  to 
the  inch. 

Some  welds  of  steel  were  about  unit  strength  and  some  of 
iron  were  above  unit  strength. 

A  number  of  these  bars  had  upsets,  however,  and  the  upset 
does  not  seem  to  have  increased  the  strength  very  much. 

When  electric  welding  was  first  tried  out  there  was  serious 
complaint  that  the  welds  were  burnt,  spongy,  and  weak.  This 
was  due  to  the  fact  that  the  metals  were  melted  together  and 
were  not  worked.  The  welding  machines  with  automatic  swage 
blocks  prevent  crystallization  at  the  weld,  as  does  also  hammer- 
ing after  welding.  The  weld  is  still  liable  to  be  weak  on  the 
edge  of  the  heating  radius.  Many  joints  that  will  hold  at  the 
weld  will  break  an  inch  either  side  because  the  heat  has  destroyed 
the  properties  of  the  metal. 


PART  III— HOT-FLAME  WELDING 


THE  OXY-ACETYLENE  PROCESS 

General. — Lest  the  variations  in  practice  and  the  variety  of 
apparatus  about  to  be  described  should  prove  confusing,  it  is 
well  to  state  that  the  oxy-acetylene  welding  process  depends  on 
the  high  heat  of  combustion  of  oxygen  and  acetylene.  The 
apparatus  primarily  consists  of: 

1.  Apparatus  for  storing  or  generating  oxygen. 

2.  Apparatus  for  storing  or  generating  acetylene. 

3.  A  burner  or  blowpipe,  with  leading  tubes,  for  the  combus- 
tion of  oxygen  and  acetylene. 

This  is  the  simple  story,  of  which  there  are  many  details. 
The  advantages  and  limitations  of  the  processes  here  described 
are  as  follows: 

1.  The  apparatus  is  fairly  light,  easily  portable,  and  can  be 
installed  permanently. 

2.  For  repair  work,  the  cost  is  light  and  the  results  satisfactory. 

3.  On  account  of  the  intense  heat  of  the  flame,  any  substance 
or  metal  can  be  melted  locally  at  once. 

4.  The  high  heat  of  the  flame  represents  a  limitation  in  so 
far  as  it  is  difficult  to  adjust  and  dangerous  to  use  unless  the 
operator  knows  his  business. 

5.  The  weld,  being  a  melt-weld,  is  subject  to  oxidation  and 
carbonization  from  the  flame,  and  to  crystallization  on  cooling. 

The  merits  of  the  oxy-acetylene  process  greatly  outweigh  its 
possible  faults.  There,  is  no  process  that  will  compare  with  it 
for  welding  job  work  of  all  kinds  of  metals  and  for  repair  work. 

The  present  use  of  the  oxy-acetylene  flame  in  welding  and 
autogenous  soldering  is  the  outcome  of  the  discoveries  of  many 
experimenters.  It  is  a  step  beyond  the  oxy-hydrogen  process: 
the  flame  has  an  opproximate  temperature  of  3500  deg.  Cent., 
while  the  oxy-hydrogen  is  about  2250  deg.  Cent.  But  this  high 

73 


74  WELDING 

heat  and  the  explosive  nature  of  acetylene  complicate  the  prob- 
lem. Special  apparatus  had  to  be  devised;  special  instructions 
worked  out  for  its  use  in  practice.  As  one  writer  states,  its 
practical  value  was  at  first  overestimated  by  those  interested  in 
it.  And  when  obstacles  arose  their  ardor  was  checked  and  the 
process  suffered  a  temporary  relapse.  At  the  present  writing, 
however,  the  oxy-acetylene  process  is  in  a  state  of  rapid  develop- 
ment, and  it  has  passed  the  critical  stage.  It  is  a  recognized 
repair  and  welding  process.  It  is  being  used  to  weld  or  solder 
almost  all  the  metals,  both  to  themselves  and  to  one  another; 
it  is  also  used  to  cut  through  steel  and  iron  plate,  bars,  etc.,  with 
six  times  the  rapidity  of  a  saw. 

There  are  several  items  in  the  apparatus  for  this  process  that 
have  advanced  its  use.  One  of  them  is  the  compounds  for  pro- 
ducing oxygen  in  situ  and  at  less  expense  than  by  the  ordinary 
electrolytic  process.  The  Industrial  Oxygen  Company  of  New 
York  sold  until  recently  a  powder  called  "Epurite,"  probably 
sodium  dioxide,  which  produced  oxygen  when  wet  with  water. 
In  1906  the  Industrial  Oxygen  Company  withdrew  this  com- 
pound and  advanced  a  second,  called  "  Oxygenite."  Oxygenite 
necessitates  special  combustion,  cleaning  and  storing  tanks, 
but  cost  of  these  is  small  in  comparison  with  the  cost  of  an  elec- 
trolytic plant,  and  brings  it  into  competition  with  the  storage 
oxygen  made  by  the  electrolytic  and  liquid-air  processes. 

The  Davis-Bournonville  Company  have  recently  adopted 
the  potassium-chlorate  method  of  generating  oxygen  in  cases 
where  tanked  oxygen  is  inconvenient.  As  with  Oxygenite,  special 
tanks  are  required  for  generating,  washing,  and  storing.  Their 
oxygen  compound  is  not  combustible  and  requires  the  external 
heat  of  a  gas  flame.  Fuller  particulars  of  these  two  chlorate 
processes  are  given  on  pages  86  and  87. 

Since  1880  industrial  oxygen  has  been  sold  in  increasing  quan- 
tities by  the  firms  using  apparatus  for  the  electrolysis  of  water. 
France  and  Germany  have  been  specially  active  in  projecting 
methods.  The  processes  of  Schuckert,  Garuti,  Schoop,  and 
Schmidt  are  worthy  of  mention.  In  late  years  oxygen  obtained 
by  the  Linde  liquid-air  process  has  come  into  competition  with 
electrolytic  oxygen.  It  is  most  largely  used  in  this  country,  while 


THE    OXY-ACETYLENE    PROCESS  75 

the  company  claims  to  supply  90  per  cent  of  the  world's  demand 
for  oxygen. 

Acetylene  was  discovered  in  1837.  It  was  nrst  recognized  as  a 
valuable  illuminant,  more  especially  in  France,  where  it  is  used  by 
hundreds  of  municipal  plants  at  the  present  day.  France  is 
also  foremost  in  oxy-acetylene  welding  inventions,  among  the 
most  important  being  those  of  Fouche. 

Acetylene  can  now  be  had  in  two  forms:  stored  acetylene  in 
steel  cylinders,  such  as  are  used  for  carbon  dioxid;  and  calcium 
carbid,  which  produces  acetylene  when  wet  with  water,  accord- 
ing to  the  formula  — 


Stored  acetylene  was  originally  a  dangerous  commodity.  It 
was  liable  to  explode  under  pressure.  The  railroads  objected  to 
handling  it.  So  the  acetylene  producer,  calcium  carbid,  held 
the  market.  The  gas  was  generated  at  the  place  where  it  was  to 
be  used  and  kept  in  a  tank  under  less  than  10  pounds'  head.  In 
1897,  the  acetone-absorption  process  was  patented,  'and  since  then 
stored  acetylene  has  been  in  active  competition  with  the  carbid 
(see  p.  92). 

At  the  present  writing  a  repair  shop  desiring  to  set  up  an  acety- 
lene welding  department  is  offered  a  number  of  alternatives  : 

1.  The  acetylene  can  be  bought  in  storage  tanks  or  it  can  be 
generated  from  the  carbid. 

2.  The  oxygen  can  be  bought  in  storage  tanks  or  it  can  be 
generated  from  Oxygenite  or  by  the  other  chlorate  method. 

3.  Oxgyen  can  be  dispensed  with  and  atmospheric  air  sub- 
stituted.    For  this  purpose  a  pressure  pump  and  air  gasometer  are 
needed.     Under  the  second  head  it  might  be  added  that  oxygen 
could  be  produced  by  the  electrolysis  of  water.     But  this  would 

require  a  large,  costly  outfit,  running'  up  into  thousands. 
Under  the  third  head,  oxygen  air  and  acetylene  are  sometimes 
used  in  a  three-way  burner. 

Apparatus  and  Gases.  —  The  Torch.  —  The  first  oxy-acetylene 
torch  was  invented  by  Mr.  Edmond  Fouche,  who  at  the  time  was 
general  manager  of  the  Campagnie  Francaise  de  PAcetylene 
dissous. 


76 


WELDING 


As  they  were  using  compressed  acetylene  in  acetone,  it  was 
very  easy  with  acetylene  under  pressure  to  get  the  proper  mixture 
when  used  with  oxygen  under  pressure. 

A  couple  of  years  later  Fouche  went  with  another  company, 
which  was  controlled  by  Javal.  But  as  they  were  not  handling 
compressed  acetylene,  but  only  generators  using  gas  under  a 
normal  pressure,  Fouche  went  ahead  and  devised  a  new  oxy- 
acetylene  burner  under  the  principle  of  an  injector,  which  with  the 
oxygen  under  pressure  coming  from  a  small  tube  into  a  larger, 
would  produce  a  suction,  by  this  absorbing  acetylene  in  enough 
quantity  to  produce  a  very  hot  flame.  So  this  is  where  the  first 
two  torches  originated — high-  and  low-pressure. 


FIG.  33. — Low-pressure  torch  for  oxy-acetylene.     Industrial  oxygen  company. 


There  is  a  certain  defect  in  both  these  torches.  The  high- 
pressure  torch  mixes  in  the  long  tube  as  the  two  gases  are  forced 
together  near  the  handle,  and  when  the  tip  of  the  burner  gets 
overheated  in  case  of  a  flash  back,  you  get  a  back  fire  in  the 
whole  length  of  the  tube;  in  which  case,  if  the  operator  is  not 
quick  in  cutting  off  the  flow  of  gases,  he  runs  a  chance  of  melting 
part  of  his  torch.  As  for  the  low-pressure  torch,  the  defect  is  in 
depending  entirely  on  the  suction  made  by  the  injector,  which 
very  often  does  not  carry  enough  acetylene  gas,  making  an  oxidiz- 
ing flame  which  prevents  the  metal  from  uniting  properly  and 
making  the  weld  very  weak. 


THE    OXY-ACETYLENE    PROCESS 


77 


The  house  of  A.  Boas  Rodrigues  &  Company,  of  Paris,  after 
looking  over  both  systems,  went  to  work  to  devise  a  third  torch, 
which  as  far  as  possible  would  remove  some  of  the  objections  of 
the  high  and  low  pressure.  By  making  a  medium-pressure 
injector  type  of  torch,  having  the  acetylene  under  at  least  3 
pounds'  pressure  or  a  little  more,  they  could  force  in  a  surplus  of 
acetylene  so  as  to  remedy  the  defect  of  the  low-pressure  system, 
which  depended  only  on  the  injector. 

Moreover,  back-firing  was  not  troublesome  in  this  medium- 
pressure  torch,  because  the  gases  were  mixed  an  inch  from  the 
nozzle.  If  the  torch  back-fired,  the  operator  could  tell  at  once 
by  the  roaring  sound.  If  he  did  not  turn  off  the  flame  at  once,  the 


en 


FIG.  34. — High-pressure  oxy-acetylene  torch  and  replaceable  tips  (Davis-Bournorr 

ville  Company). 

tip  would  be  burned,  but  not  the  torch.  The  tip  could  be  un- 
screwed and  replaced. 

The  present  low-pressure  torch  (Fig.  33)  also  mixes  its  gases 
a  short  distance  from  the  tip  of  the  nozzle. 

The  nozzles  of  all  oxy-acetylene  torches  suffer  in  time  from 
the  intense  heat  of  the  flame.  Constant  back-firing,  caused  by 
holding  the  torch  too  close  to  the  work,  will  soon  burn  out  the  tip. 
Pieces  of  melted  metal  will  get  in  the  tip,  and  should  be  removed 
carefully.  The  burner  is  a  very  sensitive  tool. 

The  up-to-date  torch  is  a  handy  affair  with  cocks  at  the  handle 
end  to  turn  the  gases  on  and  off  and  a  small  detachable  tip  or 
burner  at  the  nozzle  end.  The  gases  are  mixed  near  the  orifice 
in  the  low-pressure  torch.  In  the  high-pressure  torch  the  gases 
are  mixed  in  the  tip  (Fig.  35).  In  both  torches  the  acetylene  is 


WELDING 


first  passed  through  a  packing  of  asbestos,  wire  gauze,  etc.,  with 
handle  which  prevents  a  flash  back  into  the  generator,  on  the 
principle  of  the  Davy  lamp.  The  torches  are  in  several  stand- 
ard sizes,  each  with  five  or  six  graded  detachable  tips.  An 
extra  oxygen  tube  can  be  clamped  on  the  burner  when  used  for 
cutting  metals.  Special  cutting  torches  (Fig.  36)  are  now  made. 


FIG.  35. — Diagram  of  replaceable  tip  of  high-pressure  torch  (Davis-Bournonville 

Company). 

A  new  cutting  head  is  screwed  into  the  torch  head.  The  pure 
oxygen  jet  flows  through  the  center  and  in  front,  and  behind 
this  are  two  small  heating  flames,  four  in  all.  With  this  torch 
it  is  possible  to  cut  in  any  direction. 

To  summarize,  there  are  at  present  in  use  in  this  country  three 
torches : 

i.  The  original  Fouche  torch,  improved,  in  which  the  gases 
are  mixed  as  they  enter  the  haft. 


/          2         5 

FIG.  36. — Cutting  torch  attachment  (Davis-Bournonville  Company). 

2.  The  low-pressure  torch  (also  invented  by  Fouche)  in  which 
the  oxygen  injected  under  pressure    draws    acetylene   with    it 

(Fig.  33). 

3.  The  high-pressure  torch  (French  medium  pressure)  with 
acetylene  up  to  15  pounds  and  oxygen  stepped  down  from  120 
atmospheres  to  one  or  two  atmospheres  (Fig.  35). 


THE    OXY-ACETYLENE    PROCESS 


79 


Each  torch  claims  its  advantages,  and  to  number  them  would 
be  to  simply  give  the  talking  points  of  the  competing  firms,  without 
effect. 

The  Low-pressure  Torch  (The  Linde  Air  Products  Co.) 


Oxygen 

Acetylene 

Blow- 

Approximate 
thickness  of 

Approximate 
consumption 

Approximate 
consumption 

Foot  run 

Approximate 
cost  per  foot 

pipe 
No 

sheet  or  plate, 

cubic  feet 

cubic  feet 

per  hour 

run,  includ- 

inches 

per  hour 

per  hour 

ing  labor 

3 

& 

4 

2* 

30 

$  .012 

4 

A 

6 

3f 

21 

.021 

5 

I 

10 

6 

15 

•037 

6 

T36 

16 

10 

6 

.125 

7 

1 

25 

15 

4 

.256 

8 

I 

36 

22 

3 

•456 

10 

5 

45 

28 

2 

.827 

NOTE — For  copper  plates  larger  blowpipes  are  required  than  for  steel  plates  of 
corresponding  gauge. 

Another  authority  estimates  25  per  cent,  additional  of  each 
gas  for  the  same  thickness  of  plate.  The  high-pressure  torch  uses 
about  the  same  volume  of  gas,  with  the  oxygen  and  acetylene  in 
the  proportion  of  i .  28  to  i. 

Miscellaneous  Apparatus. — Besides  the  apparatus  already 
touched  on,  there  are  pressure-reducing  valves  on  all  of  the  pres- 
sure tanks.  These  may  be  set  by  the  turning  of  a  handle  to  any 
constant  pressure  required;  the  dial  shows  the  pressure  (Fig.  38). 

Both  systems  have  water  valves  in  both  gas  tubes,  to  prevent 
the  back  pressure  of  either  gas  in  case  of  accident.  For  instance, 
in  the  low-pressure  system,  if  the  oxygen  should  accidentally 
flow  back  into  the  acetylene  tube,  it  would  get  as  far  as  the  valve 
which  would  let  it  out  into  the  air  instead  of  into  the  acetylene  tank. 
This  prevents  explosions.  "The  action  of  hydrolic  back-pres- 
sure valve  is  apparent  from  figure  37.  The  cocks  on  the  acety- 
lene pipe  from  the  gas  holder  is  connected  to  the  inlet  at  B,  and 


8o 


WELDING 


Water  Priming  Cup 


Service  Line  Inlet 


Outlet 


the  acetylene  pipe  leading  to  the  blowpipe  is  connected  to  the 
outlet  C.  D  is  a  priming  cup  through  which  water  can  be 
poured  into  the  chamber  until  it  overflows  at  the  cock  F.  The 
cock  on  the  service  line  at  B  must  be  closed  while  the  chamber 
is  being  filled  with  water.  When  water  shows  at  the  cock  F,  it 

must  be  closed  and  the  cock  at  B 
opened.  The  valve  is  then  in 
working  order. 

"The  pipe  G,  leading  from 
below  the  seal  at  E  to  priming  cup, 
is  made  of  sufficient  length  to  hold 
a  column  of  water  equal  to  the 
pressure  in  the  acetylene  holder, 
which  would  be  equal  to  not  less 
than  12  inches  of  water,  and  in  no 
case  should  exceed  20  inches. 

"In  cases  where  two  or  more 
blowpipes  are  worked  from  the 
same  acetylene  supply  pipe,  a 
separate  back-pressure  valve  should 
be  employed  for  each  welding 
station." 

The  companies  furnish  twenty 
or  more  feet  of  hard-rubber  tubing, 
wire-wound. 

Goggles  for  the  eyes  are  ad- 
vised, both  to  protect  them  from  the  bright  light  and  from 
flying  sparks. 

Electrolysis  of  Water. — When  water  is  decomposed  by  electroly- 
sis, it  gives  2  volumes  hydrogen,  i  volume  oxygen. 

The  electrolyte  is  a  dilute  solution  of  sodium  or  potassium  hy- 
droxid;  oxygen  rises  from  the  positive  and  hydrogen  from  the 
negative.  If  the  gases  are  collected  as  mixed  oxygen  and  hydro- 
gen in  the  gasometer,  it  is  called  detonating  gas.  This  is  the  gas 
that  was  first  used  in  the  oxy-hydrogen  blowpipe  (see  page  117). 
Detonating  gas  is  handy  for  blowpipe  work,  but  it  is  dangerous. 
It  is  the  most  readily  combustible  mixture  of  the  two  gases,  and 
if  the  torch  backfires  there  will  be  an  explosion.  To  prevent 


FIG.  37. — Diagram  of  safety 
water  seal,  to  protect  the  acetylene 
supply  (the  Linde  air  products 
company). 


THE    OXY-ACETYLENE    PROCESS 


8l 


this  a  safety  water-seal  was  introduced  in  the  leading  tube,  or 
the  blowpipe  handle  contained  a  chamber  packed  with  fine  rods 
or  gauze  or  asbestos  wool  to  imitate  the  idea  of  the  Davy  safety 
lamp. 

The  railroads  will  not  handle  detonating  gas,  and  it  is  not 
manufactured  except  privately.  In  the  electrolysis  of  water 
nowadays  a  diaphragm  placed  between  kathode  and  anode  sepa- 
rates the  gases.  Of  these  gases  the  oxygen  is  of  the  greater 
commercial  importance. 


FIG.  38. — Oxygen  constant-pressure  regulator. 

Oxygen  is  colorless,  odorless,  non-poisonous,  and  supports 
combustion  with  hydrogen,  acetylene,  producer  gas,  etc. 

Since  1880  rapid  progress  has  been  made  in  the  manufacture 
of  nearly  pure  oxygen  and  hydrogen  by  the  electrolysis  of  water. 
Abroad,  it  is  the  main  source  of  these  two  gases,  especially  since 
1900.  In  America  there  is  but  one  electrolytic  industrial  plant. 
The  Linde  oxygen  practically  controls  the  market. 

Among  the  successful  commercial  processes  in  Europe  are 
6 


82 


WELDING 


those  using  the  patents  of  Schmidt,  Schuckert,  Garuti,  Schoop, 
and  Hazard-Flamand.  The  Schuckert  apparatus  is  as  follows: 

11  It  consists  of  a  cast-iron  tank,  containing  a  number  of  cast- 
iron  electrodes  in  various  chambers  separated  by  diaphragms, 
extending  from  the  top  downward  about  three-fourths  the  depth 
of  the  cell,  the.  gases  being  conveyed  through  a  pipe  system  to 
separators,  whence  the  wash-water  is  returned  to  the  electrolytic 
cells. 

"The  electrolyte  is  a  20  per  cent,  solution  of  caustic  potash. 
The  cells  are  embedded  in  a  sand  layer  about  2  or  3  inches  in 
thickness,  arranged  to  protect  the  apparatus  from  heat  radiation, 
the  temperature  of  the  electrolyte  being  maintained  at  about 
75  deg.  Cent.  This  is  said  to  be  the  most  satisfactory  temperature, 
as  the  lowest  voltage  is  required  at  this  temperature  for  decom- 
posing the  electrolyte.  The  pressure  is  from  2  to  3  volts,  and 
the  various  cells  are  connected  in  series  very  much  the  same  as 
a  battery  of  accumulators.  The  hydrogen  and  oxygen  gases 
when  generated  at  the  electrodes  are  conducted  through  pipes 
to  separate  gasometers  or  tanks  for  storage." 

From  97  to  99  per  cent,  oxygen  is  claimed  for  this  plant, 
which  is  that  of  the  Schuckert  Co.,  Niirnberg,  Germany. 

Another  process,  the  Hazard-Flamand  is  also  described  in 
detail  in  the  Electro-Chemist  and  Metallurgist2  of  the  British 
Faraday  Society.  The  table  of  relative  outputs  at  different 
current  values  is  given  below. 


The  Hazard-Flamand  Cell 


Volts  applied 

Current 

Yield  of 

Yield  of  O2 

Per  cent,  of  theoretical 

at  voltameter 
terminals 

in  amps. 

O2  grams 
per  hr. 

grams  per 
kw.-hr. 

energy  efficiency  (213.07 
grams  per  kw.-hr.) 

2.1 

243 

72.0 

141.7 

66.5 

2-3 

265 

79.0 

129.6 

60.7 

2.8 

323 

96.2 

106.3 

5°-5 

1  Electrochemical  and  Metallurgical  Industry,  F.  C.  Perkins,  May,  1906. 

2  Electro-chemist  and  Metallurgist,  June,  1904. 


THE    OXY-ACETYLENE    PROCESS  83 

"  In  considering  the  fourth  and  fifth  columns,  it  must  be 
born  in  mind  that  hydrogen  is  also  liberated,  of  double  the  volume, 
but  of  1/8  the  weight.  In  other  words,  with  an  e.  m.  f.  of  "2 .  i 
volts,  each  voltameter  produces  1.8  cu.  ft.  of  oxygen  per  hour 
and  3 . 6  cu.  ft.  of  hydrogen,  of  the  respective  approximate  weights 
of  72.0  and  9.0  grams."1  The  article  goes  on  to  state  that  while 
2 .  i  volts  is  theoretically  most  efficient,  2 . 4  gives  best  practice. 
The  oxygen  is  99  per  cent,  pure  and  the  hydrogen  in  proportion. 

Manufacturers  of  electrolytic  gases  claim  that  their  oxygen 
is  much  purer  than  that  of  other  processes.  Oxygen  by  the 
chlorate  process  is  contaminated  with  carbon  dioxid,  often 
over  10  per  cent.  Liquid-air  oxygen  contains  from  one  to  five 
per  cent,  nitrogen.  The  impurities  of  electrolytic  oxygen  are  a 
few  per  cents,  of  hydrogen,  a  little  chlorin,  and  water  vapor.  In 
laboratory  determinations  these  impurities  sometimes  determine 
which  kind  of  oxygen  shall  be  used.  For  welding  and  soldering, 
the  gases  should  be  pure  for  the  sake  of  keeping  harmful  im- 
purities from  burning  into  the  metal. 

The  first  cost  of  installation  of  an  electrolysis  plant  is  very 
great  and  may  reach  as  high  as  $25,000,  exclusive  of  maintenance 
cost.  For  this  reason  very  few  industries  would  find  it  worth 
while  to  install  such  a  plant  for  welding  purposes.  In  Europe 
these  installations  are  most  often  separate  concerns  for  the  manu- 
facture and  sale  of  stored  oxygen  and  hydrogen. 

For  further  information  about  electrolysis  of  water  the  reader 
is  referred  to  "The  Electrolysis  of  Water,"  by  Engelhardt,  trans- 
lated by  Richards,  1904. 

Storage  Oxygen. — Oxygen  can  be  bought  in  steel  cylinders. 
There  are  two  industrial  processes  at  present  for  making  oxygen. 
It  can  be  drawn  from  the  atmosphere  by  the  liquid-air  method 
or  it  can  be  produced  by  the  electrolytic  decomposition  of  water. 
This  latter  method  to  which  there  are  many  variations  is  largely 
used  in  Europe.2  The  patents  for  the  former  method  are  owned 
and  operated  under,  in  this  country,  by  The  Linde  Air  Products 
Company. 

By  the  Linde  process   the  atmosphere  is  compressed   by  a 

1  June,  1904. 
2  "Electrolysis  of  Water,"  Victor  Engelhardt,  1904. 


84 


WELDING 


double-stage  pump  up  to  1800  pounds.  This  eompression  raises 
the  temperature  i  deg.  Fahr.  for  every  2  atmospheres  pres- 
sure. The  compressed  air  is  cooled  by  ice  and  salt  (for  small 
plants)  or  by  ammonia  (for  large  plants).  If  this  air,  then, 
at  1800  pounds  and  about  15  deg.  Cent.,  be  expanded,  the  tem- 
perature will  drop  considerably.  If  some  is  expanded  on  the 
outside  of  a  cylinder  under  the  same  pressure,  the  air  in  the 
cylinder  will  be  lowered  in  temperature  and  will  liquefy  because 
it  is  under  pressure.  Liquid  air  consists  of  approximately  80 
per  cent,  nitrogen,  critical  temperature, — 149  deg.  Cent. ;  and  20 
per  cent,  oxygen,  critical  temperature, — 119  deg.  Cent.  The 
oxygen  is  then  separated  by  fractional  distillation  similar  to  the 
rectification  of  spirits. 

Storage  oxygen   can  be  obtained   in  cylinders  of  sizes  and 
weights  shown  in  the  following  table: 

Oxygen  in  Cylinders  (The   Linde  Air  Products  Co.) 


Contents  in 
cubic  feet 

Approximate  weight 
in  pounds  (empty) 

Price  of  cylinder 
with  valve 

Rent  per  week 
after  the  first  month 

51 
25 
50 

6 

38* 
62 

$   6.50 
8.50 

12.00 

$0.50 
°-7S 

100 

132 

20.00 

1.  00 

The  oxygen  is  under  pressure  of  120  atmospheres.  It  is 
guaranteed  95  per  cent,  pure,  the  residue  being  nitrogen.  As 
nitrogen  is  inert  and  not  in  sufficient  quantity  to  absorb  heat  or 
retard  action,  its  presence  is  negligible. 

These  tanks  may  be  rented  and  the  oxygen  bought  or  both 
gas  and  tank  bought  outright.  In  either  case  the  company  will 
recharge  them,  subject  to  certain  conditions.  On  account  of  the 
very  high  pressure,  the  cylinders  are  annealed  at  least  once  in 
four  years,  and  are  carefully  inspected  and  labeled  on  charging. 
Each  tank  must  have  reducing  valves  and,  when  in  use,  pressure 
gauges.  The  railroads  receive  them  charged  as  second-class 

size  of  cylinder  cannot  be  hired. 


THE    OXY-ACETYLENE    PROCESS  85 

merchandise,  and  discharged  as  fourth  class,  and  also  on  account 
of  the  pressure. 

The  factor  of  safety  is  large  with  these  tanks,  but  nevertheless 
they  must  be  kept  in  a  cool  place.  In  the  heat  of  the  direct  sun's 
rays  the  pressure  will  greatly  increase. 

The  present  price  of  this  stored  oxygen  is  from  two  and 
one-half  to  four  cents,  depending  on  the  quantity  bought.  Rent 
is  charged  on  the  tanks  after  the  first  month.  This  is  exclusive 
of  transportation.  The  advantage  of  having  a  large  volume  of 
oxygen,  in  small  bulk,  when  a  generator  is  unhandy  or  expen- 
sive, is  very  apparent.  The  principal  disadvantage  is  the  possi- 
bility of  leakage,  which  is  a  variable  factor.  Datum  is  not  at 
hand,  but  it  is  common  opinion  that  tanked  oxygen  is  at  least 
five  per  cent,  purer  than  that  produced  by  the  chlorate  process. 

Oxygenite. — "Oxygenite"  is  the  name  given  to  the  oxygen- 
producing  powder  sold  by  the  Industrial  Oxygen  Co.  Its  main 
constituents  are  potassium  chlorate  and  manganese  dioxid  in  the 
probable  proportion  of  100  to  13  by  weight.  To  this  is  added  a 
small  percentage  of  carbon  in  the  form  of  lamp-black,  to  support 
and  assist  combustion.  The  powder  is  a  fine  gray  sand  in  texture ; 
wetting  it  will  not  diminish  its  oxygen-producing  ability,  though 
it  will  cause  it  to  cake  and  harden.  It  is  accepted  by  the  railroads 
at  the  merchandise  rates  and  is  safe  to  handle. 

One  pound  of  Oxygenite  when  ignited  with  a  match  burns 
with  the  production  of  oxygen  and  carbon  dioxid,  producing 
about  4  cubic  feet  of  the  gas.     The  oxygen  is  produced  accord- 
ing to  the  reactions 
2KClO3+heat  =  2KCl+3O2and  3MnO2 +heat  =  Mn3O4 +O2. 

The  principal  function  of  the  manganese  dioxid  is  to  reduce 
the  temperature  of  occlusion  and  to  prevent  the  chlorate  from 
melting  and  flashing.  As  a  good  portion  of  the  oxygen  is  con- 
sumed by  the  carbon,  carbon  dioxid  gas  forms  a  large  percentage 
of  the  resultant  gas.  This  is  washed  out  of  the  gas  by  passing  it 
through  a  solution  of  sodium  or  potassium  hydroxid.  The 
reaction  continues  up  to  200  pounds'  pressure  and  takes  less  than 
three  minutes. 

Figure  39  is  a  diagram  of  the  apparatus  in  position.  It  con- 
sists of  a  combustion  chamber,  a  washing  tank  in  which  pebbles 


86 


WELDING 


are  drowned  in  the  caustic  solution,  and  a  gasometer.  The  func- 
tion of  the  pebbles  in  the  washing  tank  is  to  cause  the  gas  that  is  let 
in  at  the  bottom  to  work  its  way  more  slowly  to  the  top  and  to 
break  up  the  bubbles.  Less  caustic  solution  is  needed,  and  such 
a  washer  takes  the  place  of  three  washers  in  which  the  solution  is 
free. 

This  process  has  its  own  special  advantages,  though  it  is 
not  cheap.  Oxygen  can  be  generated  on  short  notice  and  at  high 
pressure  without  the  aid  of  a  gas  flame  for  heating  nor  of  a  pres- 
sure pump. 


a Generator 

a1 Cover  plate 

a2_  Safety  valve 
a*_  Brace 

a4_Tightening  Screw 
a5_Outlet  for  gas 

a° Pipe  to  cleaning  device 

b  __Washer  and  cooler 
I)1— Inlet  for  gas 
b2_Funnell  to  stopcock 
b3— Drainage  tap 
bl_Pipe  to  storage  cylinder 
c — Storage  Cylinder 
c!_  Entry  valve 
c2_Pressure  gauge 

c3_Outlet  valve  to  blowpipe 
c4_  Fixture  for  reducing  valve 
c5 Drainage  pipe 


FIG.  39. — Oxygen  apparatus  using  oxygenite  (Industrial  Oxygen  company). 

Oxygenite  is  at  present  selling  at  $15  per  100  pounds. 
Since  each  pound  is  claimed  to  produce  4  cubic  feet  of  oxygen,  the 
cost  per  cubic  foot,  exclusive  of  apparatus,  operation,  and  inci- 
dental costs,  would  be  four  cents.  Storage  oxygen  is  selling  at 
present  above  three  cents  per  cubic  foot.  While  the  final  cost 
of  using  Oxygenite  is  probably  greater  than  storage  oxygen,  it  is 
able  to  compete  with  the  latter,  because  it  is  safer  to  handle  and 
can  be  kept  indefinitely. 

Oxygen  from  Chlorate. — The  Davis-Bournonville  Company 
has  recently  added  to  its  line  apparatus  for  the  production  of 
oxygen.  The  method  is  similar  to  the  Oxygenite  process,  but 
the  oxygen  mixture  is  not  combustible;  it  must  be  heated  exter- 


THE    OXY-ACETYLENE    PROCESS  87 

nally  with  a  gas  flame.  This  mixture  is  composed  of  potassium 
chlorate,  100  parts,  and  manganese  dioxid,  13  parts;  both  should 
be  fairly  pure  to  insure  a  gas  of  97  to  98  per  cent  estimated 
purity  after  three  scrubbings. 

Figure  40  shows  the  apparatus  in  position.  The  oxygen  mix- 
ture is  charged  into  the  retort,  which  should  be  as  full  as  possible 
to  exclude  ordinary  air.  The  retort  is  heated  with  a  slow  gas 
flame  so  that  the  generation  is  regular;  as  the  heating  proceeds 
the  flame  is  raised  to  drive  off  the  last  of  the  oxygen.  The  oxygen 
generated  passes  through  three  washer  tanks  filled  with  sodium 
hydroxid  solution,  and  then  into  a  gasometer.  From  the  gasom- 
eter the  gas  is  compressed  by  a  two-stage  compressor  into  pressed- 
steel  cylinders,  at  a  pressure  of  300  pounds  to  the  inch.  This 
for  the  reason  that  considerable  pressure  is  needed  to  make  a  good 
jet  flame,  especially  in  cutting  metals. 

This  method  of  generating  oxygen  takes  more  time  than  the 
Oxygenite  process;  and  it  necessitates  a  compressor  pump  while 
the  latter  does  not.  The  advantages  claimed  for  it  are:  that 
there  is  little  oxygen  lost  when  the  retort  is  recharged,  because  the 
pressure  is  low  in  all  of  the  chambers;  that  loss  from  leakage  is 
much  less;  that  the  bubbles  of  gas  being  much  more  expanded  in 
passing  through  the  hydroxid  solution  are  washed  much  more 
thoroughly. 

One  writer1  estimates  the  cost  of  the  oxygen  mixture,  when 
made  from  fairly  pure  chemicals,  at  eight  cents  a  pound.  One 
pound  producing  4  to  4  1/2  feet,  brings  the  cost  of  the  oxygen 
to  about  2.25  cents  a  cubic  foot.  This  is  exclusive  of  freight  and 
operating  charges. 

Oxone.  —  Very  pure  oxygen  can  be  generated  on  a  small  scale 
by  wetting  sodium  peroxid. 


The  Oxone  idea  is  a  recent  development  of  an  old  method. 
The  sodium  peroxid  in  fused  lumps  is  delivered  in  hermetically 
sealed  cans  to  protect  it  from  the  moisture.  Each  pound  of 
Oxone  produces  over  2  feet  of  the  gas,  at  a  price  of  from  13  to 
20  cents  a  foot.2  The  generator  (Fig.  41)  is  made  by  the  Nel- 

1  American  Machinist,  Henry  Cave. 

2  Special  Information. 


88 


WELDING 


THE    OXY-ACETYLENE    PROCESS 


89 


son  Goodyear  Company*  and  sold  by  the  Roessler  &  Hasslacher 
Chemical  Company. 

To  make  oxygen  several  holes  are  punched  in  the  top  and 
bottom  of  the  can  and  it  is  placed  in  the  generator.  The  gen- 
erator is  filled  with  water  to  the  mark,  closed  and  the  needle 


FIG.  41. — Oxone    oxygen    generator    (the    Roessler    and    Hasslacher   Chemical 

Company). 

valve  opened.  Opening  the  valve  lets  water  in  on  the  Oxone, 
and  oxygen  begins  to  come  off.  It  is  claimed  to  be  99  per  cent 
pure;  the  trace  of  water  vapor  is  removed  by  washing,  and  the 
delivered  gas  is  then  practically  pure.  The  safety  valve  of  the 
generator  is  set  at  five  pounds  and  the  delivery  valve  at  three. 


FIG.  42. — Oxygne  burner  (the  Roessler  and  Hasslacher  Chemical  Company.) 

Closing  the  needle  valve  stops  the  generating.  Soda  lye  is  the 
by-product.  In  cleaning  out  the  generator  be  careful  not  to 
get  the  strong  lye  on  the  hands  nor  clothing. 

This  oxygen  is  expensive,  very  pure,  and  the  apparatus  easily 


QO  WELDING 

portable.  Hence  it  can  be  used  to  make  gas  for  reinforcing  the 
air  in  submarines  or  under-ground  or  under-water  workings 
and  by  jewelers,  dentists,  assayers,  and  silversmiths.  For 
burning  this  oxygen  the  company  furnishes  a  special  torch 
(Fig.  42).  The  other  gas  of  combustion  is  sulfuric  ether;  or 
acetylene,  gasoline  vapor,  or  coal  ras  can  be  used.  The  oxygen- 
ether  flame  is  ideal  for  jewelers  and  dentists.  Figure  43  shows 
a  handy  furnace  for  niching  down  metals. 


FIG.  43. — Oxone  furnace  for  dentists  and  jewelers  (the  Roessler  and  Hasslacher 

Chemical  Company). 

Acetylene. — Acetylene  is  a  heavy,  combustible  gas  with  a 
strong  odor,  and  was  first  made  by  Davy  in  1837.  It  is  produced 
by  the  reaction  between  water  and  calcium  carbid  according  to 
the  formula — 

CaC2+H20  =  C2H2+CaO2 

The  principal  impurities  of  the  freshly  generated  gas  are 
ammonia  and  hydrogen  phosphid  and  sulphid.  These  are 
removed  by  washing  the  gas  in  different  solutions  which  will  react 
upon  these  gases. 

Acetylene  is  endothermic.  So  that  the  great  heat  of  its  com- 
bustion is  the  sum  of  its  endothermic  factor  and  the  factor  for 
carbon  monoxid  or  dioxid.  For  this  reason  acetylene  burns 
with  tremendous  heat  with  oxygen.  The  intense  white  light  of 
combustion  in  air  is  attributed  to  the  nascent  carbon  particles. 

Mixed  with  air,  acetylene  is  explosive  between  the  range  of 
2  per  cent,  gas,  98  per  cent,  air;  and  49  per  cent,  gas,  51  per 


THE    OXY-ACETYLENE    PROCESS 


91 


cent  air.  This  is  a  very  wide  range  and  makes  the  gas  a  trouble- 
some one  unless  used  with  care.  The  odor,  which  is  attributed 
to  a  small  proportion  of  hydrocarbons,  is  offensive,  but  helps  to 
detect  leakage.  Though  there  are  instances  of  asphyxiation  by 
this  gas,  it  has  been  shown  that  pure  acetylene  is  not  a  poison- 
ous gas. 


FIG.  430. — Diagram  of  carbid-feed  acetylene  generator. 
•  (Davis  Acetylene  Company). 


The  Acetylene  Generator. — In  repair  shops,  Where  acetylene 
will  be  needed  continually  for  the  work  at  hand,  it  is  best  to 
install  an  acetylene  generator.  One  of  the  types  approved  by  the 
underwriters  should  be  selected.  It  should  be  placed  in  a  sepa- 
rate shed  outside  of  the  shop.  This  will"  safeguard  the  workman 
and  the  building  in  case  of  accident.  Nowadays,  however, 


92  WELDING 

acetylene  can  be  used  with  perfect  safety,  provided  there  is  ordi- 
nary good  sense  employed  in  the  installation  and  use  of  it. 

There  are  two  general  types  of  generators:  one  in  which 
powdered  or  granular  calcium  carbid  is  fed  into  water,  the  other 
in  which  water  is  dropped  upon  the  carbid.  The  reaction  gen- 


FIG.  44. — Diagram  of  hopper  and  feed  mechanism.     Davis  carbid-feed  acetylene 

generator. 

erates  considerable  heat.  This  is  the  element '  of  danger.  For 
this  reason,  perhaps  the  safer  generator  is  the  style  first  named,  in 
which  the  carbid  would  be  quenched  in  water  while  giving  off 
the  gas.  One  part  of  carbid  will  boil  six  parts,  by  weight,  of 


THE    OXY-ACETYLENE    PROCESS  93 

water.  Furthermore,  water-feed  generators  give  off  gas  long 
after  the  water  is  stopped,  and  carbid-feed  only  for  a  short  time. 

Some  carbid  contains  phosphates  which  are  decomposed 
with  the  formation  of  hydrogen  phosphid.  This  gas,  which 
comes  over  with  the  acetylene  in  small  quantities,  is  said  to 
have  a  bad  effect  on  the  metals  to  be  welded.  While  tanked 
acetylene  has  been  cleansed  of  both  hydrogen  phosphid  and 
sulphid,  the  generator  acetylene  is  not.  It  is  important  to  use 
in  the  generator  a  carbid  that  is  quite  pure  chemically.  The 
presence  of  small  quantities  of  phosphorous  can  be  easily  told 
by  the  white  smoke  it  adds  to  the  acetylene  flame.  Sulphur 
cannot  be  so  easily  detected. 

One  pound  of  lump  carbid  gives  41/2  feet  of  gas.  One 
pound  of  ground  carbid  only  4  feet,1  due  to  previous  decompo- 
sition. At  this  writing  the  cost  of  carbid  per  candlepower- 
hour  is  about  4/10  cents  for  a  24-candlepower  burner  consum- 
ing 1/2  foot  of  gas  hourly.2 

There  are  a  number  of  good  generators  on  the  market,  and 
the  purchaser  can  make  his  choice  from  them.  The  Davis 
generator  is  at  present  recommended  by  the  Davis-Bournonville 
Company.  This  is  a  lump-carbid  feeder  made  in  sizes  rangiug 
from  the  portable  size,  charged  with  20  pounds  of  carbid,  up  to 
the  largest  size  of  300  pounds'  carbid  capacity  (Fig.  44).  Lump 
carbid,  i  1/4  by  3/8  inches,  is  charged  into  the  hopper  at  the 
top,  whence  it  slides  down  an  inclined  plane  onto  a  circular  pan. 
This  pan  hangs  on  an  axle,  which  rotates  it  according  to  the 
working  of  the  overhead  motor,  and  the  carbid  is  brushed  off 
the  edge  of  the  pan  when  it  rotates.  A  pressure  diaphragm 
controls  the  feeding  apparatus.  The  operator  sets  the  diaphragm 
for  a  given  pressure  by  moving  a  weight  along  the  lever  con- 
trolling the  diaphragm.  The  pressure  of  the  gas  can  be  raised  to 
15  pounds,  is  uniform,  and  is  safe-guarded  by  a  blow-off.  The 
water  levels  are  also  maintained  by  overflow  pipes.  The  act  of 
opening  the  hopper  to  charge  the  machine  locks  the  motor,  while 
the  position  of  the  motor  weight  shows  at  once  how  much  carbid 
is  left  in  the  hopper. 

The  advantages  claimed  for  this  generator  are: 

1  Rules  of  National  Board  of  Fire  Underwriters. 

2  Davis  Acetylene  Company,  special  information. 


94  WELDING 

1.  That  being  carbid-fed,  the  resultant  gas  is  always  of   a 
safe    temperature,    because    of  the  great  excess  of  water  it  is 
quenched  in. 

2.  The  use  of  lump  carbid  ensures  slower  generation,  which 
takes  place  after  the  lumps  have  gone  to  the  bottom.     And  lump 
carbid  gives  at  least  10  per  cent,  more  gas  than  the  pulverized 
stone. 

3.  The  feed  motor  is  effective:  the  carbid  cannot  be  overfed 
and  is  fed  as  the  gas  is  needed. 

4.  The  water  levels  are  automatically  maintained. 

5.  All  parts  are  accessible. 

6.  The  charging  hopper  is  perfectly  sealed  from  leakage. 
This  generator  should  be  installed  in  a  shed  outside  of  the 

building  where  the  welding  is  carried  on.  The  shed  should 
be  of  sufficient  size  to  allow  easy  access  to  all  parts  of  the  generator, 
and  should  be  steam-heated  with  pipes  coming  from  without, 
so  that  the  water  will  not  freeze  up  in  the  winter.  No  light  or 
fire  must  be  allowed  in  or  near  the  shed,  because  of  danger  from 
explosions.  The  shed  should  be  kept  locked  and  closed  to 
all  but  the  regular  attendant,  who  is  an  experienced  hand. 

Acetylene  gas  is  much  more  dangerous  than  the  other  illumi- 
nating gases,  as  it  will  readily  explode  in  mixtures  of  more  or  less 
air  than  the  other  gases.  Accidents  are  not  so  common  now  as 
formerly,  but  happen  often  enough  to  show  that  there  is  much 
carelessness  in  the*  installation  and  management  of  generators, 
The  underwriters'  associations  of  this  country  and  abroad  are 
very  rigid  in  their  specifications  concerning  acetylene  generators. 

Dissolved  Acetylene. — Acetylene  dissociates  at  780  deg.  Cent, 
into  carbon  and  hydrogen;  under  pressure  of  two  atmospheres  or 
more,  the  gas  is  tricky  and  is  liable  to  explode.  But  acetylene 
is  readily  soluble  in  a  number  of  liquids,  among  them  acetone. 
Acetone  is  fairly  cheap^inert,  and  incombustible — very  essential 
properties.  It  boils  at  56  deg.  Cent.,  has  a  strong  affinity  for 
acetylene,  and  is  not  decomposed  by  it.  At  atmospheric  pres- 
sure and  15  deg.  Cent,  acetone  dissolves  24  times  its  volume  of 
acetylene.  At  12  atmospheres,  which  is  the  pressure  given  the 
storage  cylinders,  it  dissolves  about  300  volumes  of  the  gas  and 
increases  in  volume  50  per  cent.  The  pressure  of  such  a  tank 


THE    OXY-ACETYLENE    PROCESS  95 

is  doubled  with  every  rise  of  30  deg.  Cent.,  while  undissolved 
acetylene  triples  its  pressure  for  each  rise  of  8  deg.  Cent. 

Berthelot  and  Vielle1  experimented  with  the  solution  of  acety- 
lene in  acetone  and  found  that  it  could  not  be  exploded  with 
an  electric  spark  though  under  high  pressure.  Hutton2  says 
that,  "In  practice  1,000  liters  of  acetylene  carry  off  the  vapor  of 
0.06  liter  of  liquid  acetone" — not  an  appreciable  amount. 

All  of  the  above  characteristics  of  the  solution  recommend 
acetone  as  a  solvent  or  body  for  the  storage  of  acetylene  for 
commerce.  The  French  government  was  the  first  to  officially 
recognize  acetone  storage  tanks  as  safe.  The  railroads  of  this 
country  now  accept  the  cylinders  for  carriage  as  non-explosive. 

Acetone  storage  was  worked  out  by  the  Belgian  chemists 
Claude  and  Hesse,  and  patented  by  them  in  1897.  The  principal 
difficulty  to  overcome  was  the  factor  of  expansion  of  the  solution 
with  increased  acetylene  content,  and  the  corresponding  shrinking 
as  the  acetylene  was  drawn  out  of  the  tank.  The  cylinder  would 
be  full  at  12  atmospheres  and  only  two-thirds  full  under  normal 
pressure.  This  meant  that  a  considerable  part  of  the  tank  would 
contain  the  gas  alone,  subject  to  the  danger  of  explosion.  To 
overcome  this,  the  cylinder  was  filled  with  a  porous  or  absorbent 
body,  which  was  saturated  with  the  acetone-acetylene  solution. 
Porous  brick  or  stoneware  of  four-fifths  porosity  was  used; 
also  charcoal  cake,  bound  together  with  soluble  glass;  in  this 
country  asbestos  fiber  with  soluble  glass  binder  is  used.  These 
absorbents  will  all  carry  from  50  to  80  per  cent,  of  the  solution 
per  volume.  When  the  acetylene  is  all  drawn  off,  the  tank  is 
still  perfectly  safe  and  can  be  recharged  simply  by  passing  in 
acetylene  under  pressure. 

The  tanks  themselves  are  pressed-steel  cylinders,  such  as  are 
used  for  soda-water,  and  are  fitted  with  cocks  and  a  pressure-regu- 
lating valve.  They  are  delivered  under  10  atmospheres'  pressure, 
and  contain  about  100  volumes  of  the  gas — considerably  below  the 
saturation  content  of  acetone  at  that  pressure.  They  should  be 
kept  in  a  cool  place,  out  of  the  sunlight,  because  the  pressure 
doubles  with  30  deg.  rise  of  temperature.  If  exposed  to  too  great 


1  Elec.  and  Metal.  Industry,  March,  1903. 

2  R.  S.  Hutton,  Elec.  and  Metal.  Industry,  April,  1903. 


96 


WELDING 


heat,  the  pressure  might  rise  to  the  danger  point,  and  an  explosion 
take  place. 

Acetylene  storage  tanks  are  of  the  following  size  and  capacity : 

Acetylene  Storage  Tanks1 


Diameter 
in  inches 

Length,  inches 

Capacity,  cu.  ft. 

Weight,  pounds 

7 

24 

50 

5° 

8 

30 

80 

75 

10 

3° 

125 

i°5 

12 

36 

225 

120 

14 

48 

400 

349 

16 

48 

500 

435 

Carbid  will%  produce  about  4  cubic  feet  of  acetylene  per 
pound;  the  present  price  is  below  four  cents  a  pound.  This 
brings  the  material  cost  to  about  one  cent  per  cubic  foot  of  gas. 
Stored  acetylene  costs  about  twice  as  much,  but  its  adaptability 
is  much  greater  and  in  many  cases  much  more  than  nullifies  the 
difference.  It  is  claimed  to  be  the  purest  form  of  the  gas,  being 
practically  free  from  sulphur  and  phosphorus,  because  it  receives 
four  to  six  washings. 

Practice. — The  directions  for  the  use  of  the  oxy-acetylene 
flame  are  few  and  the  process  is  simple,  but  it  takes  a  skilled 
workman  to  get  results.  Six  months'  practice  is  none  too  long 
before  efficiency  can  be  looked  for.  It  is  one  thing  to  melt  metals 
together  and  quite  another  to  make  a  weld  of  homogeneous  metal 
in  which  strains  are  at  a  minimum.  The  companies  print  and 
issue  directions,  which  will  be  here  abstracted  and  added  to. 
Beyond  that  it  is  a  question  of  individual  gray  matter. 

The  Flame. — The  flame  is  lighted  by  first  turning  on  the  acet- 
ylene, lighting  it,  and  then  turning  on  the  oxygen.  The  acetylene 
burns  with  a  bright,  smoky  flame.  As  the  oxygen  jet  increases,  an 
indefinite-shaped  cone  appears  at  the  nozzle;  it  first  has  two  points, 
one  beyond  the  other.  More  oxygen  reduces  it  to  a  clearly  de- 

1  Henry  Cave,  The  Horseless  Age,  Dec.  2,  1908. 


HOW   TO    WELD  97 

fined  single  cone  of  blue  flame.  If  there  is  too  much  oxygen,  the 
flame  will  sputter  and  roar  and  the  point  of  the  cone  become 
ragged  and  violet-colored.  For  this  reason  the  operator  can  al- 
ways tell  by  appearance  when  his  flame  is  right.  It  is  always 
safer  to  have  too  much  acetylene,  rather  than  too  much  oxygen. 
Oxygen  will  burn  and  rust  the  metal;  acetylene  will  keep  it  from 
burning. 

The  low-pressure  flame  consumes  acetylene  and  oxygen  in  the 
ratio  of  i  to  i .  50;  the  high-pressure  in  ratio  of  i  to  i .  28. 

As  to  pressure  for  the  gases,  the  operator  will  soon  learn  by 
trial  what  pressure  of  oxygen  is  necessary  to  use  to  keep  the  flame 
from  back-firing.  The  low-pressure  torch  needs  higher  oxygen 
pressure  to  draw  in  the  acetylene;  at  least  30  pounds  for  welding 
and  125  pounds  for  cutting.  Pressure  is  regulated  by  turning 
on  the  full  initial  supply  of  the  gases  and  then  setting  the  con- 
stant-pressure regulators.  Different  kinds  of  work  may  take  dif- 
ferent pressures. 

The  hottest  part  of  the  flame  is  at  the  tip  of  the  cone  and  a 
fraction  beyond.  Never  hold  the  cone  against  the  work,  because 
it  will  burn  the  metal.  Only  the  tip  should  be  allowed  to  touch. 

HOW  TO  WELD 

To  weld,  the  operator  goes  over  the  metal  quickly  with  the 
flame  a  number  of  times.  This  will  heat  the  metal  evenly  to 
about  dull  red  heat.  If  the  work  is  stock  work  and  is  continuous, 
it  will  save  from  30  to  50  per  cent,  of  time  and  cost  to  preheat 
with  a  coke,  gas,  or  oil  fire  or  with  electricity. 

After  preheating  the  seam,  the  flame  is  circled  about  a  small 
radius  until  the  metal  softens.  Metal  is  added  and  worked  in 
with  a  "melt  bar  "  and  care  is  taken  that  the  edges  of  the  metal 
are  melted  and  perfectly  united.  The  operator  works  away 
from  his  body  and  finishes  the  work  as  he  proceeds.  With  a 
little  practice  the  seam  can  be  made  quite  smooth  and  even. 

Cast  iron  can  be  easily  welded.     It  melts  easily,  is  very  fluid, 

and  runs  toward  the  heat  of  the  flame.     Some  care  is  necessary 

to  avoid  its  running  clear  away  from  the  weld.     The  piece  to  be 

welded  must  be  held  horizontally  or  the  molten  metal  must  be 

7 


98  WELDING 

dammed.  The  melt  bar  is  cast  iron  and  should  be  low  in  sul- 
phur and  phosphorus  and  high  in  silicon.  Flux  is  sometimes 
recommended,  though  a  skillful  use  of  the  flame  and  stirring 
with  the  melt  bar  will  serve  the  purpose.  Salt  or  borax  is  a 
good  flux. 

Preheating  is  very  necessary  in  treating  cast  iron.  Heat  all 
of  the  casting  to  dull  red,  or  as  much  as  is  necessary  to  prevent 
cracking.  Coke  or  gas  fire  is  cheapest  if  there  is  much  welding 
to  be  done.  Slow  cooling  is  just  as  necessary  as  preheating. 
Annealing  may  even  be  necessary  to  adjust  the  strains. 

Wrought  iron  requires  less  care  in  preheating,  though  this  can- 
not be  neglected.  The  melt  bar  is  soft  iron.  Pure  iron  is 
sticky  and  not  very  fluid.  For  this  reason  the  softened  metal 
can  be  stirred  into  place  with  the  end  of  the  melt  bar.  It  is  a 
good  thing  to  hammer  and  work  wrought-iron  joints  while  cooling 
so  as  to  build  up  the  structure  that  the  melting  has  destroyed. 

Steel  also  works  well  with  this  flame.  The  metal  becomes 
soft  but  does  not  run.  It  burns  easily  in  excess  of  oxygen. 
Cave1  states  that  auto  frames  can  be  welded  from  beneath  with 
the  high-pressure  torch,  because  the  melted  steel  adheres  well 
and  is  spread  wherever  wanted  by  the  flame.  He  recommends 
commercial  soft-steel  wire  for  the  melt  bar.  Low-carbon,  open- 
hearth  steel  is  best  for  the  melt  bar,  because  on  cooling  it  is 
more  liable  to  retain  its  strength. 

Steel  welds  should  also  be  hammered  if  possible  on  cooling, 
and  then  annealed.  Even  then  a  high-carbon  steel  will  suffer 
severely  within  the  heating  radius.  The  weld  joint  can  be 
reinforced,  but  the  heat  always  extends  beyond  the  reinforce- 
ment. In  spite  of  reinforcing,  working,  and  annealing,  high 
carbon  and  tool- steel  joints  will  lack  strength  and  the  elastic 
limit  will  be  lowered. 

Heavy  copper  articles  are  seldom  welded  with  this  flame, 
though  the  results  are  just  as  good  as  by  electricity.  Because  of 
high  heat  conductivity  a  larger  flame  or  more  time  is  needed, 
and  because  of  the  rapid  oxidation  an  excess  of  acetylene  must 
be  maintained  in  the  flame. 

Working  is  very  necessary  in  the  case  of  drawn  and  rolled 

1  Iron  Age,  Sept.,  1909. 


HOW    TO    WELD  99 

copper,  in  order  to  restore  the  structure;  but  it  would  be  well  for 
the  operator  to  determine  whether  the  copper  is  cold-short  or  hot- 
short  before  hammering,  otherwise  he  may  fracture  the  weld. 

Brass  is  a  special  problem.  The  hot  flame  begins  to  volatilize 
the  zinc  of  the  alloy  before  the  melting  point  is  reached.  Hence 
some  covering  or  reducing  flux  should  be  used,  such  as  powdered, 
fusible  silicates,  borax,  glass,  etc.  The  flux  melts  and  covers  the 
surface.  Bronze  needs  similar  treatment. 

Aluminum  is  also  troublesome  because  it  becomes  pasty,  and 
when  finally  liquid  will  oxidize  rapidly.  As  soon  as  the  metal 
at  the  joint  softens  it  is  added  to  from  the  melt  bar,  and  the  pasty 
metal  is  then  worked  into  the  seam  or  patch  with  an  iron  spatula. 
Pasty  aluminum  can  be  manipulated  like  solder.  •  When  the 
joint  cools  it  will  be  as  strong  as  the  body  of  the  piece,  if  properly 
worked.  If  not  properly  worked,  layers  of  the  oxid  film  will  be 
enclosed  in  the  joint  and  will  weaken  it.  This  film  will  easily 
come  to  the  surface  with  working. 

Preheating  is  very  important  because  aluminum  also  conducts 
heat  very  rapidly.  Slow  cooling  of  castings  is  necessary  to  pre- 
vent tension  and  cracking.  Hammering  will  give  a  dense,  tough 
structure,  but  the  operator  must  beware  not  to  hammer  aluminum 
between  600  deg.  Cent,  and  655  deg.  Cent.,  the  melting  point, 
because  it  will  crumble  under  the  hammer. 

Other  metals  and  alloys  can  be  welded,  and  will  be  in  the  future 
as  this  process  becomes  better  known.  In  automobile  and  ma- 
chine repair  shops  a  great  variety  of  new  alloys  are  constantly 
coming  up,  and  the  repair  man  finds  that  each  requires  indi- 
vidual treatment,  both  in  handling  the  flame  and  in  the  use  of 
fluxes.  As  this  flame  has  a  possible  heat  of  over  3000  deg.  C.,  it 
can  be  toned  down  to  any  desired  intensity  by  the  use  of  air  in 
some  excess,  though  at  lower  temperature  it  will  be  increasingly 
oxidizing. 

Similarly,  two  different  metals  may  be  welded,  provided  their 
melting  points  are  not  more  than  500  deg.  Cent,  apart  and  pro- 
vided they  will  form  an  alloy.  Metals  of  widely  separated  melt- 
ing points  will  also  weld,  but  the  joint  may  be  uncertain.  Metals 
that  will  not  alloy,  as  iron  and  zinc,  make  a  poor  weld.  If  one 
metal  is  crystalline  and  the  other  not,  the  weld  will  be  poor,  as  with 


100 


WELDING 


steel  and  wrought  iron.  But  in  contradiction  to  this  general  state- 
ment, Cobleigh1  mentions  a  case  where  pieces  of  steel  and  copper 
were  welded  on  a  piece  of  cast  iron.  It  looks  as  though  skilled 
labor  will  soon  be  able  to  weld  almost  any  metals  or  alloys  that 
will  melt. 

Pressure  Regulating 
Valves 


FIG.  45. — Diagram  of  high  pressure   oxy-acetylene   system,  using  storage  tanks. 

There  appear  to  be  no  limits  to  the  sizes  of  work  this  flame 
can  weld.  Plates  of  No.  20  gauge  can  be  butt-welded,  while  cast 
iron  14  inches  thick  has  been  joined.  Large  work  is  commonly 
chamfered  or  beveled  at  about  45  deg.  angle  to  ensure  equal 

melting.  When  plates  are  butt- 
welded,  the  Linde  Air  Products 
Company2  recommends  spread- 
ing the  far  ends  of  the  plates  2  1/2 


Weld  begins  here 


FIG.  46. — Showing  adjustment  of 
plates  for  welding. 


,00 


FIG.  47. — Correct  bevels  for 
strong  weld. 


per  cent,  of  their  length,  as  shown  in  figure  46.  This,  because 
the  cooling  and  shrinking  of  the  metal  at  the  weld  constantly 
draws  the  plates  together.  The  strongest  weld  can  be  obtained  by 
beveling  both  edges  and  welding  both  sides  of  the  plate  (Fig.  47). 

1  Iron  A%e,  Jan.  7,  1909. 

2  Catalog  C, 


HOW    TO   WELD 


101 


Although  you  are  sure  you  have  the  correct  mixture  in  your 
flame,  examine  your  work  from  time  to  time.  If  the  metal  hard- 
ens with  a  spongy  or  scaly  structure,  it  is  burnt  and  you  have 
too  much  oxygen. 

Always  add  about  one-third  thickness  of  metal  to  the  weld  to 
gain  an  equal  strength.  If  it  is  necessary  to  machine  down  the 
joint  to  unit  thickness,  you  need  not  count  on  more  than  75  per 
cent,  strength  for  that  joint,  though  it  may  run  as  high  as  95 
per  cent. 

As  with  all  melt- welds,  the  oxy-acetylene  weld  is- benefited  by 
annealing  and  the  elasticity  partly  restored. 


Time  in  minutes  per  meter 

a-JLK-itljrjLJLJ 

/ 

*/ 

// 

^ 

t 

y' 

/ 

^ 

/ 

/ 

/ 

^ 

^ 

12          34          567           89         Id 

Thickness  in  mm. 

FIG.  48.  —  Diagram  of  comparative  welding  with  gas  and  acetylene  (L.  L.  Bernier). 


Adaptability.  —  As  already  stated,  this  process  is  essentially 
a  repair  welding  process.  We  have  a  very  hot  flame  which  we  can 
adjust  easily  along  a  large  range  of  sizes.  The  flame  can  be 
turned  on  or  off  at  will  and  can  be  carried  into  any  corner  of  the 
work.  The  flame  is  practically  a  hand  tool.  For  this  reason  the 
several  firms  promoting  this  process  are  selling  easily  portable 
apparatus  for  use  in  machine  shops,  shipyards,  automobile 
repair  stations,  and  manufactories  where  repair  work  is  daily 
necessary.  The  Fore  Shipbuilding  Company,  the  Newport 
News  Shipbuilding  Company,  the  Pullman  Car  Company, 
National  Tube  Company,  United  States  Navy  Department,  and 


102  WELDING 

many  of  the  big  machine  shops  of  the  country  are  using  this 
process  for  both  repair  and  stock  welding. 

Chemical  and  metallurgical  laboratories  can  use  the  flame  to 
advantage  to  get  very  high  local  heats.  It  is  suggested  that  the 
flame  may  be  adapted  to  assay  work  where  the  rock  is  very 
refractory.  The  cost  and  time  needed  to  get  a  high  heat  in  an 
assay  furnace  is  often  considerable.  With  this  flame  the  expen- 
sive and  fragile  muffle  might  often  be  dispensed  with. 

The  oxy-acetylene  flame  is  now  being  used  to  weld  steel  tubes 
for  bicycles,  automobile  frames,  steel  tanks  and  cylinders  for 
carbonic  acid,  etc.,  angle  iron,  etc.  Quite  a  bit  has  been  written 
about  the  probability  of  acetylene-welded  boilers  displacing  riv- 
eted boilers.  Gas-welded  boilers  have  been  made,  but  as  yet 
welded  boilers  are  not  recognized  as  safe,  though  there  is  no 
doubt  they  can  be  made  so.  Figures  50  to  57  show  different 
kinds  of  repair  and  job  work  done  by  this  process. 

In  the  hands  of  skilled  workmen  the  oxy-acetylene  flame  is  a 
safe  tool  for  repairing  such  ticklish  work  as  boiler  plates,  steel 
containing-cylinders,  steel  tubing,  etc.  But  on  the  other  hand, 
tests  of  welds  have  sometimes  shown  that  the  metal  was  either 
fatally  burnt  or  carbonized.  It  would  be  the  height  of  folly  to 
allow  a  green  hand  to  repair  a  boiler  with  this  flame.  In  France 
an  eight  months'  apprenticeship  is  required  before  the  work- 
man is  allowed  to  touch  repair  work.  It  is  doubtful  if 
acetylene  welding  will  replace  riveting  for  boilers  or  structural 
iron  and  steel  where  the  strains  are  tensional.  A  good  weld 
is  much  stronger  and  also  quite  a  bit  cheaper  than  a  single- 
or  even  a  double-riveted  joint.  But  a  riveted  joint  is  of  a 
definite  known  strength,  and  a  weld  may  be  porous  and  brittle 
under  a  good,  smooth  surface,  and  may  be  less  than  25  per  cent, 
strength. 

Typical  Welds  and  Repairs. — The  following  instances 
of  boiler  repair  are  given  by  L.  L.  Bernier,  in  his  "Autogenous 
Welding  of  Metals": 

"Repairing  Cracks  Steamer  'Eugene  Pereire'  of  the  French 
Line: 

"The  boiler  furnaces  of  the  mail  steamer  Eugene  Pereire  of 
the  French  Line  had  numerous  horizontal  cracks  above  the 


HOW    TO   WELD 


I03 


grate  bars.     There  were  about  100  of  these,  and  in  two  of  the 
furnaces  they  extended  from  end  to  end  of  the  corrugations. 

"  It  had  been  attempted  to  stop  the  worst  of  these  by  plugging; 


FIG.  49. — Repairing  with  the  oxy-acetylene  torch  (Davis-Bournonville  Company) 

but  it  would  have  been  necessary  to  renew  several  furnaces, 
which  would  have  detained  the  steamer  for  two  months  and 
caused  great  expense.  All  the  cracks  were  wedged  open  with 


FIG.  50. 


FIG.  51 


FIG.  50. — High-pressure  tank  for  U.  S.  Navy.  Ends  and  seams  welded  and 
3/4"  flange  welded  to  end.  Material  1/2  inch  thick,  size  36  x  30  3/4  inches. 
Tested  to  250  Ibs. 

FIG.  51. — Steel  tubes  welded  to  shell. 

chisels  and  welded;  all  repaired  parts  were  annealed  with  burners. 
In  two  spots  where  there  were  several  adjoining  cracks,  a  part  of 
the  furnace  was  cut  out  and  replaced  by  a  welded  piece.  No 


104 


WELDING 


leak  was  observed  at  any  of  the  100  places  so  repaired  at  the  hydro- 
static or  steam  tests. 

"  Only  the  sweating  of  a  few  drops,  caused  by  trifling  lamina- 
tions, were  discovered,  and  a  little  calking  restored  the  water- 
tightness  at  such  spots.  The  work  lasted  three  weeks  and  cost 
$300.  From  the  month  of  March  of  that  year  the  steamer 
has  been  on  the  Algiers  voyage,  which  is  very  trying  for  boilers 


FIG.  52. — Galvanized  tank  witn  oxy-acetylene  welded  end  piece  (heat  expansion 
would  shear  rivets). 

on  account  of  its  shortness,  the  fires  being  banked  and  boiler 
temperatures  changed  so  frequently.  No  trouble  has  been  ex- 
perienced with  any  of  the  welded  parts." 

"  Repairing  Corroded  Parts  on  the  '  Cholon' : 

"  Oxy-acetylene  welding  may  be  used  to  add  metal  directly  to 
the  surfaces  of  plates,  to  repair  corroded  spots,  such  as  are  fre- 
quently found  in  various  parts  of  boilers.  The  flame  of  the 
blowpipe  is  directed  upon  the  plate,  and  when  the  latter  begins 


HOW    TO    WELD 


to  melt  the  workman  presents  to  the  flame  a  bar  of  soft  steel 
about  7  by  7,  which  melts  and  fixes  itself  in  drops  on  the  corroded 
surface. 

"  The  repairs  of  the  Marsa,  already  referred  to,  give  a  sample 
of  the  value  of  the  welding  process,  but  the  work  performed 
on  the  Cholon,  of  the  Compagnie  des  Chargeurs  Reunis,  from 
August  20  to  September  20,  1906,  presents  a  still  more  striking 
case. 


FIG.  53. — Welded  cylinder.     Oxy-acetylene  process. 


"The  eighteen  corrugated  furnaces  of  this  steamer  were 
badly  eaten  away  on  the  surface.  There  was  corrosion  on  each 
side  and  for  some  distance  above  the  grate  bars. 

"The  work  was  difficult  to  perform,  as  the  workmen  were 
compelled  to  be  inside  of  the  boilers;  and  were  inconvenienced 
by  the  heat  of  the  blowpipe  flame;  and  the  places  to  be  welded 
were  lower  than  the  workmen's  footing;  10,000  cubic  feet  of 
dissolved  acetylene  and  as  much  of  oxygen  were  used;  about  200 
pounds  of  steel  were  used  to  cover  the  corrosions  and  restore 
the  plates  to  their  original  thickness.  This  work,  at  a  total 


io6 


WELDING 


cost  of    $2,400,  avoided  the  replacing  of  eighteen  furnaces,  as 
originally  ordered  by  the  government  inspectors." 

Acetylene  Welding  versus  Riveting. — The  approximate 
strength  of  single-riveted  boiler  plate  is  55  per  cent.;  of  double- 
riveted,  70  per  cent.  L.  L.  Bernier,  in  the  Boiler  Maker,  gives 
the  ratio  of  cost  of  acetylene  welding  with  a  generator,  compared 


Fro.  54. — Top  section  of  broken  crank  case  with  broken  arms. 

with  double  riveting,  as  seven  to  twelve.  The  cost  of  triple 
riveting  is  not  given,  but  it  would  still  further  increase  the  discrep- 
ancy. Besides  being  cheaper,  the  acetylene- weld  is  absolutely 
leak  proof,  a  great  advantage  over  a  riveted  joint. 

On  the  other  hand,  an  apparently  sound  acetylene-weld  may 
have  a  tensile  strength  of  25  per  cent,  instead  of  95,  and  may  be 
crystalline  and  brittle;  whereas  the  riveted  joint  is  of  certain 


HOW    TO    WELD 


107 


strength.  In  the  present  state  of  the  art  it  would  be  a  mistake 
to  advocate  the  acetylene-welding  of  boilers  of  any  size,  though  for 
small  containers  and  tubes  that  can  be  rolled  and  annealed  the 
riveted  and  brazed  joint  is  being  rapidly  superseded  by  the 
acetylene-weld.  But  oxy-acetylene  repair  welds  are  now  fre- 
quently made  on  cracked  and  corroded  boilers.  Cracks  are 


FIG.  55. — Engine  crank  case  with  welded  arms. 

first  laid  open  by  a  partial  heating,  until  their  full  extent  is 
known.  Then  they  are  welded  by  the  flame  and  a  melt  bar, 
working  up  from  the  bottom  of  the  crack.  Where  the  plate  is 
full  of  cracks  or  is  corroded  deeply,  a  section  of  the  plate  is  cut 
out  with  a  cutting  flame  and  a  fresh  plate  patch  is  welded  in. 
Boiler  repairing  requires  very  careful  preheating,  hammering  of 


108  WELDING 

the  weld  and  subsequent  annealing  of  the  plate  surrounding 
the  weld. 

Repairing  Defective  Castings. — One  of  the  important 
possibilities  of  this  process  is  in  the  repairing  of  defective  castings 
fresh  from  the  foundry.  Even  in  the  most  careful  foundry  prac- 
tice the  scrap  heap  is  always  a  very  expensive  mountain  to  the 
foundryman.  If  he  can  keep  down  the  heap  he  can  increase  his 
profits.  With  the  oxy-acetylene  flame  all  kinds  of  defects  of 


FIG.  56. — Welded  aluminum  engine  bed. 

castings  can  be  repaired.  Broken  pieces  can  be  put  together  an 
imperfect  pieces  built  up  and  repaired.  As  with  other  repair 
work,  a  preheating  torch  or  furnace  would  be  needed  for  pieces 
of  any  size,  even  though  they  were  of  low-carbon  steel.  After 
the  acetylene  flame  had  done  its  work,  an  annealing  furnace 
would  be  necessary.  Both  the  oxy-acetylene  process  and  the 
thermit  process  (see  page  121)  offer  a  solution  for  the  economical 
reduction  of  the  scrap  heap. 

But  there  is  one  serious  limitation  to  the  possibility  of  using 
the  oxy-acetylene  flame  or  thermit  to  repair  a  new  casting.     Such 


HOW   TO   WELD 


I09 


a  casting  cannot  honestly  be  called  new.  The  repair  may  make 
it  stronger  than  a  perfect  piece,  but  the  fact  remains  that  it  is  a 
repaired  piece.  The  foundryman  may  or  may  not  tell  his  cus- 
tomer what  he  is  selling  him,  according  to  his  standard  of  honesty. 
It  may  be  difficult  to  convince  that  customer  that  he  is  getting  a 
first-class  article  and  should  pay  full  price  for  it.  Many  cus- 
tomers would  not  accept  it  under  any  sort  of  guarantee.  Again,  it 
might  be  equally  damaging  to  the  foundryman  if  it  became  known 
that  he  sold  as  perfect  castings  which  had  to  be  repaired,  if  he  did 


FIG.  57. — Welded  auto  frame.     Weld  is  at  the  white  line  near  the  base  of  the  steering 

handle. 

so  without  telling  the  customer.  Again,  it  is  poor  practice  for 
the  printer,  the  potter,  the  foundryman,  etc.,  to  accept  knock- 
down prices  for  a  doubtful  product,  and  so  admit  its  inferiority. 

The  fact  remains  that  this  flame  offers  a  fairly  cheap  way  of 
redeeming  defective  castings.  The  founder  must  use  his  judg- 
ment in  employing  it. 

How  to  Cut  Metals.— Besides  its  use  in  melting  metals 
for  welding,  it  has  recently  been  found  that  the  oxy-acetylene 
flame  will  cut  through  metals.  The  importance  of  this  discovery 
is  not  yet  realized.  Wrought-iron  and  steel  plate  can  be  cut 
through  as  fast  as  a  carpenter  can  tear  through  scantling  with  a 


IIO  WELDING 

rip-saw;  cast  iron  not  so  readily.  Other  metals  and  alloys, 
such  as  aluminum,  brass,  etc.,  can  also  be  cut.  Jottrand  is 
credited  with  this  discovery. 

Cutting  is  effected  by  both  the  melting  and  the  burning  of  the 
metal.  In  the  case  of  iron,  the  ordinary  flame  heats  it  to  bright 
heat,  when  an  extra  oxygen  cock  is  turned  on.  Iron  burns  with 
evolution  of  great  heat  in  the  presence  of  oxygen.  At  the  same 
time  this  heat  is  partly  transmitted  to  the  iron  in  front  of  the  jet, 
while  the  jet  blows  out  the  iron  oxid  and  molten  metal  wherever 
it  strikes.  When  the  cutting  flame  is  at  its  best  it  entirely  oxi- 
dizes the  iron,  blowing  out  a  clean  narrow  cut.  Cutting  is  a 
spectacular  process,  due  to  the  shower  of  slag  sparks  that  fall 
from  the  cut. 

While  the  cutting  may  be  done  with  the  oxygen  flame  alone, 
after  the  iron  is  red-hot,  modern  practice  uses  a  preheating  torch 
to  which  an  additional  oxygen  jet  is  attached.  The  torch  is  the 
ordinary  medium-  or  low-pressure  torch,  while  the  oxygen  jet  is 
above  125  pounds.  Several  firms  are  selling  such  torches  (see 
Fig.  36). 

The  torch  is  first  adjusted  to  a  welding  flame,  while  the  cock 
of  the  oxygen  jet  is  closed.  The  operator  points  the  flame  at 
the  edge  of  the  metal  to  be  cut.  As  soon  as  bright  red  heat  is 


L 


5  ft.  length 


r 


FIG.  58. — Iron  girder  cut  by  oxy-acetylene  flame. 

reached,  he  moves  the  flame  inward  about  half  an  inch  and  turns 
on  the  full  oxygen  jet  which  strikes  the  edge  just  heated.  Mean- 
while the  flame  is  heating  the  new  part.  For  different  thick- 
nesses of  metal  he  can  use  a  given  oxygen  tip,  of  which  each 
torch  has  three. 

The  rate  of  cutting  varies  with  the  thickness  of  the  plate,  and 
the  skill  of  the  operator.  Roughly,  this  flame  takes  from  1/5  to 
i/ 10  the  time  in  cutting  a  given  section  of  steel  that  two  men 
working  with  a  metal  saw  would  take.  There  are  several  records 


HOW    TO    WELD  III 

of  4-inch  plates  cut  by  it,  while  the  companies  claim  6  and  8 
inches  for  it. 

An  exhibition  of  flame-cutting  was  given  recently  by  M. 
Bournonville.  During  the  extension  work  for  the  new  New  York 
subway  approaches  to  the  Williamsburg  Bridge  it  was  found 
necessary  to  cut  through  a  3/8-inch  I-beam  of  steel,  whose  di- 
mensions appear  in  figure  58.  The  entire  cutting  took  21  1/2 
minutes.  This  gives  the  reader  an  idea  of  the  efficiency  of  this 
process. 

This  flame  should  be  used  to  cut  any  metal  that  resists  the 
metal  saw.  Should  it  fail  to  oxidize,  it  would  melt  its  way  through. 
An  oxy-acetylene  cutter  should  be  an  adjunct  to  every  repair 
shop  of  any  size.  It  would  be  found  invaluable  in  cutting  away 
badly  wrenched  metal  work  and  in  cutting  and  working  on  parts 
of  any  machine,  such  as  an  automobile,  where  a  special  fixture 
was  to  be  fastened.  For  besides  its  ability  to  cut,  this  flame  can 
be  made  to  pierce  rivet  holes  straight  through  one-inch  steel  in 
less  than  two  minutes. 

This  flame  has  found  its  way  into  the  railroad  repair  shops, 
one  of  which  uses  it  to  cut  away  twisted  metal  on  "gondola'' 
coal  cars.  These  cars  are  light,  strong,  and  durable,  and  are 
rapidly  displacing  the  wooden  cars.  But  loss  by  wreckage  is 
great  and  a  bad  wreck  of  gondolas  is  a  very  difficult  thing  to 
handle.  The  cars  are  often  shapeless  masses  caught  together  by 
the  force  of  the  impact,  and  difficult  to  separate.  It  has  some- 
times been  necessary  to  clear  the  track  with  dynamite.  Two 
storage  tanks  and  several  burners  carried  on  the  wrecking  train 
would  be  of  great  assistance  in  such  a  wreck. 

Every  auto  repair  shop  of  any  size  will  probably  have  one  of 
these  oxy-acetylene  outfits  in  a  few  years.  The  same  may  be  said 
of  ordinary  machine  shops,  car  shops,  boiler  shops,  etc. 

A  table  of  cutting  costs  has  been  worked  out  by  the  Davis- 
Bournonville  Company,  which  is  here  appended.  Oxygen  is 
reckoned  at  three  cents  a  foot,  acetylene  at  one  cent,  and  labor  at 
thirty  cents  an  hour. 


112 


WELDING 
Approximate  Cost  of  Cutting  Steel 


a 

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up  to  $•" 

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is* 

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14  to  18  Ibs. 

125  Ibs. 

60 

•30 

.0447 

2 

4 

i"  to  ij" 

12 

IS* 

75  ' 

14  to  18  Ibs. 

125  to  150 

50 

•  30 

3-13 

.0627 

2 

5 

ii"  up 

18 

23 

95  . 

18  to  22  Ibs. 

150  to  175 

40 

•30 

4.02 

.1005 

Costs. — It  is,  of  course,  impossible  to  give  costs  in  an  empirical 
way.  In  the  first  place,  improved  methods  of  generating  the  two 
gases  are  still  being  advanced,  as  well  as  improved  apparatus  for 
production  and  storage.  The  prices  of  raw  material  fluctuate,  and 
the  cost  of  labor  is  increasing  irregularly.  But  most  serious,  no  two 
men  are  likely  to  use  the  same  amount  of  gas  nor  take  the  same  time 
for  a  specific  job;  nor  .would  one  workman  be  apt  to  repeat  his 
performance.  It  at  once  appears,  that  outside  of  catalog  prices 
for  apparatus,  cost  estimating  is  as  difficult  as  in  the  printing  trade. 

I  have  given  cost  data  at  several  points  which  must  be  taken 
with  a  little  salt.  Before  purchasing  oxy-acetylene  plants,  it 
would  always  be  in  order  to  get  estimates  and  statements  from  the 
several  firms  handling  this  line;  these  should  advise  the  kind  of 
outfit  for  the  work  at  hand. 

The  table  of  costs  worked  out  by  the  Davis-Bournonville 
Company  is  appended. 

Approximate  Cost  of  Oxy-acetylene  Welding 

Oxygen  at  3  cents,  acetylene  at  i  cent  per  cubic  foot;  labor  30  cents  per  hour. 


3 

3 
R 

a 
H 

Thickness 
of  metal 

Consumption 
of  acetylene 
per  hour 

Consumption 
of  oxygen 
per  hour 

Proper  pressure 
in  pounds  for 
oxygen 

i! 

3! 

is 

j  ^ 
1 

Ii 
Ji 

O 

Is 

o   o 
"3  u 

ii 

n    0 

a! 

11 
o  .« 

i 

A  to  Je 

2.8   feet 

3.  6  feet 

8  to  10  Ibs. 

50  feet 

$0.30 

.436 

.0087 

2 

A  to  A 

4-5 

5-7    " 

I  O  tO   12      " 

30 

0.30 

.516 

.0172 

3 

&  to    i 

7-5 

9-7    " 

12  tO   14      " 

25 

0.30 

.666 

.0266 

4 

J    to    i 

ii.  7      " 

IS-      '.' 

14  to  18    " 

16     " 

0.30 

.867 

.054 

5 

i    to  A 

18. 

23- 

I  8  tO  22      " 

10       ' 

0.30 

1.17 

.117 

6 

T\  to  ^ 

25- 

32. 

20  tO  25      " 

7      ' 

0.30 

i-Si 

.216 

7 

TV  to    \ 

32.5      " 

41-5    " 

22  tO  2  7      " 

5      ' 

0.30 

1.87 

•  374 

8 

i  upward 

48.5 

62.      " 

24  to  30    " 

2.64 

HOW    TO    WELD 


The  following  table1  is  intended  to  show  the  costs  and  effi- 
ciency of  the  three  principal  welding  flames.  Costs  are  figured 
on  the  basis  of  generator  acetylene  one  cent  a  foot;  compressed 
acetylene,  two  and  one-half  cents;  oxygen,  three  cents;  hydrogen, 
one  cent;  coal  gas,  one  and  one-quarter  cents.  I  have  reduced 
the  estimated  temperatures  to  reasonable  limits. 


- 

Oxy-acetylene 
mixture 

Oxy-hydro- 
gen  mixture 

Oxy-coal 
gas  mixture 

Number  of  B.  T.  U.  obtained 
by  complete  combustion  of 
one  cubic  foot  of  gas  
Temperature  (Fahr.)  obtained 
by  combustion  of  the  mix- 
ture (approx  ) 

*S7° 
3000°  C. 

290 

2000°  C 

616 

1700°  C 

Cubic  feet  of  oxygen  required 
to  burn  one  cubic  foot  of  gas 
to  obtain  the  best  welding 
flame  (from  practical  tests 
made)  •  

i-3o2  i.7o3 

O.2C 

0.67 

Cubic  feet  of  oxygen  required 
to   obtain    1000   B.   T.   U. 
with  a  welding  flame  
Cubic  feet  of  heat-producing 
gas  required  to  obtain  1000 
B.  T.  U.  with  -a   welding 
flame  

0.765  2  i.oo3 
0.59 

0.86 
3-44 

1.09 
1.63 

Cost  of  1000  B.  T.  U.  (cents) 

f2.892  3.59  3  (gen- 
j  erator    acetylene) 
3.782   4.39  3    (dis- 
solved acetylene) 

5-92 

"  4.20 

Chemistry  and  Thermics. — A  definite  formula  should  not  be 
laid  down  for  the  oxy-acetylene  flame  as  used.  This  for  the 
reason  that  the  products  of  combustion  vary  with  different  pro- 
portions of  the  gases  and  in  different  parts  of  the  flame.  Lewes4 

1  Bulletin  Technologique,  Sept.,  1907. 

2  Medium-pressure  torch  used. 

3  Low-pressure  torch  used. 

4  "Acetylene,"  Vivian  Lewes,  iqoo,  D.  120. 

8 


114  WELDING 

gives  the  probable  maximum  of  the  flame  as  lying  between  3100 
deg.  Cent,  and  4000  deg.  Cent.  This  forbids  the  formula  of 
Davy, 

2C2H2  +sO2  =  2H2O  +4CO2, 

because  water  is  dissociated  at  only  780  deg.  Cent.  Beltzer 
makes  it 

C2H2+02  =  2CO+H2, 

while  Beaupre  allows  less  than  one  part  monoxid  in  100,000  of 
the  residual  gas.1  Presuming  that  none  of  the  carbon  forms 
monoxid,  Beaupre  states  that  oxids  of  nitrogen  are  formed  in 
small  quantity  and  ozone  in  very  appreciable  amount.  Le 
Chatelier2  gives  hydrogen,  carbon  dioxid,  and  monoxid  as  the 
principal  gases  from  burning  7.74-17.37  parts  acetylene  in  100 
parts  air.  It  is  quite  likely  that  the  layer  of  hydrogen  on  the 
outer  surface  of  the  flame  is  partly  burned  to  water,  and  partly 
dissipated. 

Theoretically,  the  acetylene  requires  about  2.5  parts  of  oxy- 
gen. But  practice  proves  that  this  gives  an  oxidizing  flame. 
So  the  proportion  of  i  part  acetylene  to  i .  50  oxygen  is  recom- 
mended. Recently  M.  Bournonville's  experiments  have  shown 
that,  with  his  torch  in  working  order  and  the  flame  the  proper 
color  and  shape,  the  proportion  fell  as  low  as  i  of  acetylene  to 
i .  28  oxygen.3  Repeated  trials  confirmed  these  figures.  How- 
ever, this  seems  a  small  matter.  The  flame  should  be  decidedly 
reducing,  but  should  not  be  so  charged  with  excess  acetylene 
that  it  will  deposit  carbon. 

The  temperature  commonly  ascribed  to  the  oxy-acetylene 
flame  is  3500  deg.  Cent.  Acetylene  is  composed  of  92.3  parts 
carbon  and  7 .  7  hydrogen,  according  to  its  symbol.  Its  tempera- 
ture of  dissociation  is  780  deg.  Cent.,  according  to  Lewes;4  on 
burning,  its  heat  value  is  310,500  cal.,  according  to  Thomsen.5 
This  great  heat  need  not  all  be  attributed  to  the  burning  of 
nascent  carbon,  for  the  gas  is  endothermic,  requiring  47,700  cal. 
for  its  formation.6 

1  Comptes  rendu.,  1906,  142,  165-6. 

2  Comptes  reniu.,  121,  1144. 

3  Special  information. 

4  "Acetylene,"  Vivian  Lewes,  1900. 

5  Thermochem.  Unters.,  4,  74. 

6  Roscoe  and  Schorlemmer,  Vol.  I,  p.  770.     "Treatise  on  Chemistry." 


HOW    TO    WELD  115 

Le  Chatelier1  gives  formulas  of  reaction  and  temperatures  for 
three  different  mixtures  of  acetylene  with  air,  and  shows  that  a 
minimum  of  air  produces  carbon  dioxid  and  water;  and  an  excess 
of  air,  carbon  monoxid  and  hydrogen.  In  any  case,  the  flame 
if  properly  handled  is  reducing  beyond  the  blue  cone,  which  should 
never  be  allowed  to  more  than  touch  the  work  in  hand.  Such 
hydrogen  as  remains  unburned  in  the  flame  is  claimed  to  form 
a  protecting  envelope. 

Testing. — It  is  natural  to  expect  that  a  unit  cross-section  of 
an  oxy-acetylene  welding  will  not  be  of  equal  strength  with  the 
metal  before  welding.  The  metal  has  been  melted,  perhaps 
oxidized  or  carbonized  slightly,  and  has  cooled  quickly.  If  the 
weld  is  not  pounded  or  worked  while  cooling,  the  chances  are 
that  the  metal  has  crystallized  and  is  brittle.  The  average  oxy- 
acetylene  weld  is  more  brittle  than  the  metal  itself,  and  has  from 
60  to  95  per  cent,  of  the  tensile  strength.  To  make  a  weld  as 
strong  as  the  unwelded  metal,  an  upset  or  extra  thickness  of  metal 
must  be  added  to  the  weld.  Some  writers  make  the  ridiculous 
statement  that  the  weld  is  even  stronger  than,  the  original  metal. 
This  is  only  possible  when  a  large  joint  is  made.  And  in  any 
event  the  elasticity  is  much  reduced  even  when  the  joint  has 
been  hammered  or  pressed. 

But  for  its  purpose,  when  carefully  made,  the  acetylene  weld 
is  strong  enough  and  compares  favorably  with  welds  made  by. 
other  processes.  Tubing,  automobile  frames,  boiler  patches,  and 
miscellaneous  joints  which  have  successfully  withstood  the  excess- 
ive shocks,  stresses,  or  pressures  demanded  of  them,  all  attest 
to  the  ability  of  the  acetylene  welder  to  do  good  work. 

THE  OXY-HYDROGEN  PROCESS 

General. — The  oxy-hydrogen  flame  is  the  first,  historically, 
of  the  high-temperature  flames.  It  was  used  long  before  the 
discovery  of  industrial  electrolysis  of  water  or  the  production  of 
oxygen  by  liquid-air  process.  The  first  flames  were  fed  with 
oxygen  generated  from  potassium  chlorate  and  manganese  dioxid 
or  from  the  decomposition  of  sodium  and  potassium  peroxids 

1  Comptes  rendu,  121,  1144. 


Il6  WELDING 

with  water  or  similar  methods,  and  with  hydrogen  from  zinc  and 
hydrochloric  acid  or  similar  methods.  Both  the  hydrogen  and 
the  oxygen  can  be  used  independently  for  the  following  combi- 
nations, the  hottest  first: 

1.  Oxy-hydrogen. 

2.  Oxygen-coal  gas. 

3.  Air-hydrogen. 

Apparatus. — The  first  efficient  apparatus  was  devised  by 
Newman,1  who  used  pure  oxy-hydrogen  (detonating  gas)  under 
2  or  3  atmospheres'  pressure.  The  burner  was  a  glass  tube 
about  4  inches  long,  of  i/8o-inch  bore.  The  flame  was  kept  at 
the  tip  by  reason  of  the  pressure  and  the  narrow  bore.  In 
1847,  Robert  Hare,  of  Philadelphia,  fused  2  pounds  of  platinum 
with  a  blowpipe  of  his  own  invention.  He  also  used  detonating 
gas;  and  as  a  safety  device,  to  prevent  back-fire  explosion,  a  handle 
packed  tight  with  copper  rods,  through  which  the  gas  was  forced 
to  the  tip.  This  acted  on  the  principle  of  the  Davy  lamp.  In 
1859  Deville  and  Debray  revived  this  flame  for  platinum  welding, 
and  since  then  it  has  been  employed  in  working  that  metal  and 
also,  sometimes,  for  gold  and  silver. 

At  the  present  time  the  oxy-hydrogen  flame  is  much  used  in 
laboratories  for  production  of  high  heat  and  to  a  limited  extent 
in  repair  and  boiler  shops.  It  has  long  been  the  preferred  method 
for  sealing  lead  chambers  for  sulphuric  acid  manufacture  by  the 
contact  process.  Before  the  advent  of  the  electric  arc,  bright 
light  was  obtained  by  heating  a  chunk  of  lime  in  this  flame.  This 
once  widely  advertised  light  is  almost  unknown  at  present.  Be- 
fore industrial  oxygen  and  hydrogen  were  made  by  electrolysis  of 
water,  this  flame  was  quite  expensive,  and  recently  it  has  been 
crowded  severely  by  the  oxy-acetylene  process.  But  in  platinum 
welding,  lead  soldering,  and  laboratory  research  it  holds  its  own. 

Detonating  gas  is  made  by  the  decomposition  of  water  with- 
out separating  the  resultant  gases.  It  can  be  used  for  soldering 
and  welding,  provided  the  burner  is  protected  from  back-fire,  by 
passing  the  gas  through  a  safety  chamber  filled  with  fine  porous 
material  or  guarded  by  a  water  valve.  Detonating  gas  is  com- 
paratively cheap,  though  the  railroads  often  object  to  handling  it. 

1  Encyclopedia  Britannica,  Vol.  XVIII,  p.  105. 


HOW    TO    WELD 


117 


Separate  oxygen  and  hydrogen  are  to  be  preferred  on  account  of 
safety. 

The  outfit  consists  of  tanks  of  the  gases,  tubes,  and  a  burner 
(see  Fig.  59).  To  prevent  one  gas  from  flowing  into  the  other 
gas  supply  tank,  if  the  pressure  of  the  second  gas  should 
fail,  each  leading  tube  is  provided  with  a  safety  water  valve.  The 
burner  is  a  tube  in  a  tube:  the  inner  tube  carrying  oxygen,  the 


FIG.  59. — Oxy-hydrogen  blowpipe. 

surrounding  tube  hydrogen.  Both  have  cocks.  The  hydrogen 
is  first  turned  on  and  lighted;  then  turn  on  the  oxygen.  This 
burner  is  also  suited  for  oxygen-coal  gas. 

Figure  60  shows  the  air-hydrogen  torch;  the  hydrogen  is 
injected  at  the  handle  and  draws  in  air  through  holes  in  the  tip. 
The  amount  of  air  is  regulated  by  a  ring.  This  burner  resembles 
the  Bunsen  burner,  and  is  used  for  small  work,  where  great  heat 


Hydrogen 
Inlet 


,  FIG.  60. — Hydrogen-air  blowpipe. 

is  not  needed.     The  hydrogen  may  be  produced  by  the  zinc-acid 
process. 

M.  U.  Schoop,1  the  welding  expert,  recommends  the  burner 
shown  in  figure  61  for  large-scale  work.  The  torch  has  two 
chambers.  The  first  is  filled  with  oxygen.  The  hydrogen  tube 
passes  through  this  chamber  into  the  second.  The  injected 


Electrochemical  and  Metallurgical  Industry,  July,  1905. 


Il8  WELDING 

hydrogen  draws  oxygen  from  the  first  chamber  into  the  second, 
where  they  mix  before  coming  out  at  the  nozzle.  This  torch  is 
liable  to  back-fire,  but  it  gives  a  perfect  combustion  and  prevents 
free  oxygen  in  the  flame. 

The  air-hydrogen  process  is  apparently  cheaper,  but  when  it 
is  considered  that  much  less  heat  is  evolved  and  that  three  hours' 
time  are  needed  to  one  hour  for  oxy-hydrogen,  it  turns  out  to  be 
dearer.  Schoop  claims  that  it  is  more  dangerous  than  oxy- 
hydrogen.  It  is  the  preferred  flame  for  "lead  burning,"  as 
the  sealing  of  lead  seams  is  called.  C.  H.  Fay1  has  explained  the 


Oxygen 
Inlet 


Hydrogen 
Inlet 

FIG.  61.  —  Oxy-hydrogen  burner  allowing  perfect  mixing  of  the  gases. 

apparatus  and  process  in  great  detail.  He  used  apparatus  of  the 
Kirkwood  &  Herr  Hydrogen  Machine  Company,  of  Chicago. 
It  included:  an  air  gasometer;  a  hydrogen-generating  apparatus, 
using  zinc  and  sulphuric  acid;  and  a  regular  burner  with  two  cocks. 
If  the  hydrogen  was  used  under  pressure  up  to  30  pounds,  the  air 
gasometer  could  be  done  away  with,  and  air  introduced  by  in- 
jection instead. 

The  Flame.  —  Oxygen  and  hydrogen  for  combustion  are  mixed 
in  a  long-shanked  burner  at  the  lower  end  of  the  handle.  They 
burn  at  the  tip  with  a  pale  blue,  almost  colorless  flame.  The 
theoretical  formula  of  combustion  is 


Though  these  gases  will  unite  as  low  as  155  deg.  Cent.,2  the 
action  is  slow.  Explosive  ignition  of  mixtures  of  the  gases  in 
different  proportions  occurs  at  an  average  temperature  of  825  deg. 
Cent.  Richards3  gives  the  temperature  of  the  hottest  part  of  the 
flame  as  3191  deg.  Cent.,  and  of  the  air-hydrogen  flame  as 

1  "Lead  Burning,"  1905. 

2  Electrochemical  and  Metallurgical  Industry,  May,  1905. 

3  Roscoe  and  Schorlemmer,  Vol.  I,  p.  287,    "Treatise  on  Chemistry." 


HOW    TO    WELD 


119 


20IO1  deg.  Cent.  Bunsen's  experiments  gave  a  maximum  of 
2844  deg.  Cent.  The  former  temperature,  of  course,  is  not  to  be 
found  throughout  the  flame,  if  at  all.  The  actual  temperature 
is  probably  not  much  above  2000  deg.  Cent,  under  working  con- 
ditions, and  while  this  is  above  the  fusion  point  of  most  of  the 
metals,  it  is  none  too  high  when  conduction  is  reckoned  on.  The 
heating  value  of  the  hydrogen  flame  is  much  less  than  the  acetylene, 
being  67,940  calories. 

Practice. — In  using  the  oxy-hydrogen  flame  it  is  necessary 
to  use  an  excess  of  hydrogen  over  the  theoretical  amount  of  two 
volumes  to  one  of  oxygen. 
Otherwise  there  is  danger 
of  oxidizing  the  metal  sur- 
face with  hot  oxygen. 
Platinum  is  the  exception. 
This  metal  absorbs  hydro- 
gen and  swells  up.  When 

COOling,  it  OCCludeS  the  gas  FlG-  62.— Lap  welding  lead  sheets  with 

0  air-hydrogen  flame. 

and    becomes    rough    and 

pocked.  One  writer1  recommends  4  to  5  volumes  of  hydrogen 
to  i  of  oxygen  for  ordinary  welding.  This  is  so  in  the  case 
of  iron,  copper,  aluminium,  and  other  oxidizable  metals,  when 
the  unmixed-gas  type  of  burner  is  used.  But  no  such  excess  is 
necessary  where  the  gases  are  mixed  before  ignition. 

In  lighting  the  oxy-hydrogen  burner,  turn  on  two-thirds  of  the 
hydrogen  first  and  light  it,  then  turn  on  oxygen  until  you  have 
a  pale  blue  conical  flame.  Then  turn  the  hydrogen  on  full. 
If  the  burner  is  of  the  type  shown  in  figure  61,  do  not  light 
for  at  least  ten  seconds;  and  turn  the  oxygen  off  first  when 
extinguishing. 

The  air-hydrogen  flame,  being  cooler,  must  be  larger.  Hydro- 
gen is  turned  on  and  lighted  first.  The  flame  will  be  about  3 
inches  long,  pale  red,  and  will  burn  unsteadily.  Now  turn  on  air 
until  the  flame  shortens  to  2  inches  and  has  a  fixed,  pale  blue 
cone.  If  you  are  using  an  injector  air-burner,  you  regulate  the 
air  by  turning  the  air  ring. 

In  using  either  flame  do  not  bring  the  end  of  the  cone  of 

1  Electrochemical  and  Metallurgical  Industry,  May,  1909. 


120  WELDING 

oxygen  against  the  work  in  hand.  If  you  do,  you  are  liable  to 
burn  your  metal. 

The  operator  is  advised  to  use  a  flame  of  such  size  that  it  will 
not  melt  the  metal  at  once.  Slow  melting  will  make  a  better 
job,  and  the  metal  will  not  be  so  apt  to  run  away  from  the  joint 
before  he  is  prepared  for  it.  Operators  commonly  weld  a  drop 
at  a  time  as  shown  in  figure  62.  They  then  go  back  over  the 
seam  a  second  time  to  smooth  off  the  surface. 

Different  metals  require  different  treatment.  There  are  little 
points  in  the  handling  of  this  flame  that  the  operator  will  have 
to  work  out  for  himself.  Like  any  highly  efficient  tool,  it  requires 
a  skilled  workman. 

"The  time1  for  welding  i  meter  of  sheet  iron  3  mm.  in 
thickness  is  about  15  minutes,  while  for  welding  i  meter  of  sheet 
metal  of  o.  5  mm.  thickness,  it  is  from  4  to  6  minutes.'1 

1  Electrochemical  and  Metallurgical  Industry,  F.  C.  Perkins,  May,  1906. 


PART  IV— THERMIT 


THE  THERMIT  PROCESS 

General. — One  of  the  most  recent  and  successful  methods  of 
welding  is  called  the  Thermit  Process.  It  was  invented  by  Dr. 
Goldschmidt,  of  Essen,  Germany,  and  is  exploited  by  the  com- 
pany bearing  his  name.  In  this  process  a  mixture  of  aluminum 
and  oxid  of  iron  is  ignited.  The  aluminum  reduces  the  iron  from 
its  oxid,  and  evolves  an  intense  heat,  about  2500  deg.  Cent.,  or 
twice  the  temperature  of  molten  steel.  This  molten  steel,  called 
thermit  steel,  is  then  poured  around  the  metal  to  be  welded  and 
forms  a  melt-joint  that  is  very  strong  when  cold.  Its  present 
application  is  entirely  in  repairs  of  large  metal  pieces  and  in 
making  continuous  welded  railroad  track.  It  is  used  in  repair 
shops  for  mending  car  axles,  auto  and  electric  motor  cases,  broken 
and  defective  castings,  broken  parts  of  reciprocating  engines, 
broken  rudder-posts,  skegs,  and  sternposts  of  ships,  and  for  repair 
work  in  general  along  this  line.  Special  thermit  mixtures  are  being 
advocated  for  toning  up  the  melted  steel  in  the  ladle  in  foundry 
practice,  for  preventing  "piping"  of  ingots;  and  the  company  is 
using  the  strong  reducing  property  of  aluminum  in  reducing  a 
number  of  the  less  used  metals,  such  as  tungsten,  chromium,  and 
boron,  to  a  pure  metallic  state. 

Thermit  is  first  of  all  a  welding  process.  Its  good  and  weak 
points  may  be  summed  up  thus : 

1.  Simplicity  of  the  apparatus. 

2.  No  special  skill  needed  to  do  the  work. 

3.  Possibility  of   repairing  breaks  difficult  of  access  and  of 
repairing  parts  in  situ  that  would  otherwise  have  to  be  taken  out. 

4.  Possiblity  of  intense  local  heating  of  large  parts. 

5.  Time  and  money  saved  in  most  repair  work. 

6.  Possibility  of  varying  the  chemical  composition  of  thermit 
steel  so  that  its  properties  may  be  varied. 

121 


122  WELDING 

7.  It  is  at  present  limited  to  rail  welding  and  repair  work. 

8.  Only  iron  and  steel  can  be  welded. 

9.  The  cost,  though  much  lower  than  the  forge  method  of 
welding,  is  still  often  prohibitive. 

The  process  is  used  by  many  of  the  leading  railroads,  shipyards, 
and  machine  shops  of  all  of  these  countries,  both  for  repair  work 
and  for  special  jointing,  such  as  that  of  the  third  rail  of  the  Paris 
subway.  At  present  Dr.  Goldschmidt  is  trying  to  produce  chem- 
ically pure  metals  on  a  commercial  scale.  He  has  met  with 
success  in  reducing  metallic  manganese,  chromium,  tungsten, 
vanadium,  molybdinum,  boron,  etc.,  from  their  ores  and  oxids. 
This  new  field  in  metallurgy,  now  called  aluminothermics,  seems 
to  promise  as  many  new  and  interesting  possibilities  on  its 
horizon  as  did  the  experiments  of  Moissan  with  his  electric 
furnace. 

The  fundamental  idea  beneath  thermit  has  been  in  the  minds 
of  metallurgists  for  at  least  a  half-century.  In  the  year  1869,  a 
Mr.  Budd1  describes  a  process  for  reducing  the  alloyed  silicon  in 
pig  iron.  His  idea  was  to  burn  it  out  with  hematite  ore,  the 
formula  being: 


He  made  a  paste  of  hematite  and  smeared  it  over  the  bottoms 
of  the  pig  molds.  The  molten  iron,  which  appears  to  have  been 
much  too  high  in  silicon,  was  run  into  the  molds,  and  immediately 
the  silicon  began  to  burn  out  of  the  iron,  first  taking  up  the  oxygen 
of  the  hematite  mud  on  the  bottom  of  the  mold,  and  then  uniting 
with  some  of  the  iron  and  coming  to  the  top  as  a  silicate-of-iron 
slag.  Most  of  the  iron  reduced  from  the  hematite  added  itself 
to  the  pig.  Like  the  Goldschmidt  method,  this  was  the  reduction 
of  one  metal  by  the  transfer  of  its  oxygen  to  another  metal. 

The  fact  that  aluminum  has  the  greatest  affinity  for  oxygen 
has  long  suggested  it  as  a  final  reducing  agent.  And  its  steady  fall 
in  price  since  its  discovery  by  Woehler  in  1857  finally  brought  it, 
about  1895,  within  range  of  the  market.  Woehler  himself  tried 
to  smelt  chromium  from  its  chlorid  by  ignition  with  metallic 

1  Transactions  of  the  Iron  and  Steel  Institute,  1869;  "On  a  New  Process  for 
Removing  Silicon  from  Pig  Iron." 


THE    THERMIT    PROCESS  123 

aluminum.  After  an  explosively  violent  reaction,  he  found  he 
had  an  alloy  of  chromium  with  aluminum. 

A  number  of  later  attempts  were  made  to  use  aluminum  as  an 
agent  for  reducing  the  rare  metals  from  their  oxids.  Yet,  though 
it  had  an  intense  affinity  for  oxygen,  the  combustion  was  hard 
to  start,  and  when  started  was  hard  to  control.  Experi- 
menters mixed  it  as  a  powder  with  a  metallic  oxid  and 
heated  the  mixture  from  the  outside.  Finely  divided  metallic 
aluminum  will  not  burn  at  the  temperature  of  molten 
cast  irc?n.  So  that  when  the  contents  of  the  crucible  began  to 
react,  the  initial  temperature  was  already  so  high  that  the  reaction 
was  an  explosion.  Dr.  Goldschmidt  overcame  this  by  setting 
off  the  cold  powder  with  a  fuse  of  barium  peroxid,  BaO,  which 
in  turn  was  set  off  by  a  storm  match.  A  charge  of  several  pounds 
was  found  to  burn  in  less  than  30  seconds,  and  the  temperature  of 
the  mass  rose  to  an  approximate  2500  deg.  Cent.  Larger  quanti- 
ties, though  starting  to  burn  from  a  cold  and  coarsely  powdered 
sand,  often  boiled  over.  A  premixture  of  cold  steel  turnings 
remedied  this.  The  result  of  the  burning  was  an  intensely  hot 
iron  whose  composition  could  be  varied  at  will. 

The  commercial  value  of  this  invention  is  obvious.  There 
are  many  processes  and  many  emergencies  where  a  very  hot 
molten  iron  is  invaluable,  yet  where  it  is  difficult  and  expensive 
to  get  this  heat  by  any  known  means.  Take  the  case  of  a  broken 
casting  of  some  large  machine  that  would  in  the  ordinary  course 
of  repair  have  to  be  taken  apart  and  shipped  to  the  nearest  forge 
to  be  welded.  If,  however,  a  definite  quantity  of  iron,  heated  to 
twice  its  melting  point,  can  be  made  on  the  spot,  it  can  be  poured 
around  this  break  without  dismantling  the  machine.  It  will 
then  form  a  welded  union,  much  as  though  one  were  to  put  the 
butts  of  two  candles  together  and  pour  hot  tallow  over  the  joint. 
The  tallow  would  melt  into  the  candles  before  it  itself  cooled, 
and  join  the  two  with  a  homogeneous  substance. 

In  order  that  the  mechanical  aspect  of  the  thermit  weld  may 
be  clear  to  the  reader,  a  simple  case  of  rail  welding  will  be  out- 
lined. After  which  the  appliances  used  in  the  process  will  be 
described  in  detail. 

Apparatus  and  Rail  Welding. — Suppose  a  case  of  two  rails 


124  WELDING 

abutting  which  are  to  be  welded  together.  It  is  a  railway  cross- 
ing where  heavy  trains  pound.  The  weld  must  be  at  least  as 
strong  as  the  rail.  It  must  be  so  made  as  not  to  interfere  with  the 
travel  of  the  wheels  by  coming  up  over  the  head  of  the  rail.  First 
of  all,  the  rail  ends  must  be  cleaned  of  oxid  and  grease  with  a  sand 
blast  or  emery-paper  or  hydrochloric  acid.  Next,  the  rail  ends  are 
heated  to  a  dull  red  heat  with  a  kerosene  or,  preferably,  a  gasoline 
torch.  This  merely  assists  the  hot  thermit  metal  and  prevents  a 
premature  chilling  of  the  thermit  when  it  is  poured  in  the  mold. 
Two  clay  molds  are  next  clamped  on  either  side  of  the  junction. 
The  shape  of  the  interior  of  these  molds  is,  of  course,  determined 
by  the  shape  of  the  collar  which  is  intended  to  be  cast.  In  this 


FIG.  63. — Rails  before  welding.  FIG.  64. — Welded  rail,  showing 

thermit-steel  shoulder. 

case,  as  shown  in  figure  64,  the  collar  should  extend  2  inches 
over  each  rail  end.  It  shall  be  twice  as  thick  as  the  shank  of  the 
rail  and  also  the  base  of  the  rail.  It  shall  stop  short  of  the  rail 
heads,  which  shall  remain  free.  The  mold  is  constructed  so  as 
to  allow  the  molten  metal  to  be  introduced  from  the  bottom,  as 
shown  in  the  figure.  After  coming  in  from  the  runner,  at  the  bot- 
tom, the  slag  and  excess  steel  overflow  into  the  riser. 

We  have  then  two  rails  enclosed  in  a  mold  whose  capacity, 
over  the  rails  themselves,  is  known.  To  produce  enough  thermit 
steel  to  well  fill  this  mold  and  "to  allow  as  much  more  to  fill  the 
runner  and  the  riser,  take  eighteen  times  as  many  ounces  of  thermit 
powder  as  there  are  cubic  inches  of  surplus  space  in  the  mold. 

The  above  amount  is  arrived  at  as  follows:  One  cubic  inch 
of  steel  weighs  4  1/2  ounces.  Four  and  one-half  ounces  steel  is 
produced  by  twice  as  much  thermit  powder  by  weight,  or  nine 
times.  And  as  the  runner  and  riser  take  as  much  fluid  as  the 
inside  of  the  mold,  we  multiply  again  by  2  and  get  eighteen. 

When  a  wax  collar  is  first  built  on  the  joint,  the  amount  of 
thermit  should  be  thirty-two  times  the  weight  of  the  wax  used. 
The  weight  of  the  wax  used  is  found  by  subtracting  the  weight  of 


THE    THERMIT    PROCESS  125 

the  piece  of  wax  remaining  from  the  total  weight  of  the  original 
wax  lump. 

The  proper  amount  of  thermit  powder  is  poured  into  the  cone 
crucible  (Fig.  65),  and  a  spoonful  of  barium  hydroxid  is  heaped 
upon  the  thermit.  The  crucible  is  placed  with  its  tap  hole  about 
4.  inches  above  and  directly  over  the  hole  of  the  riser  in  the  mold. 
Set  off  the  barium  powder  with  a  storm  match  and  get  away  as 
soon  as  the  barium  is  caught.  The  burning  quickly  spreads  from 
the  barium  fuse  to  the  thermit,  and  in  a  fraction  of  a  minute  the 
entire  contents  of  the  crucible  are  boiling  at  a  temperature  of 
about  25oodeg.  Cent.  White  smoke,  flames,  and  drops  of  white 
hot  slag  are  ejected  during  the  combustion,  which  is  most  spec- 
tacular and  reminds  one  of  the  blowing  of  a  Bessemer  converter. 
In  working  with  thermit  is  is  well  to  wear  smoked  glasses,  as  the 
glare  of  the  reaction  and  the  hot  fluid  is  troublesome.  In  about 
thirty  seconds  the  reaction  is  completed,  but  the  crucible  should  be 
allowed  to  stand  for  a  half -minute  longer  to  enable  the  slag  to 
rise  to  the  surface.  It  is  probably  for  the  reason  that  the  slag 
does  not  have  time  to  rise  before  the  workman  taps  his  crucible 
that  the  joints  sometimes  show  blow  holes  and  faulty  structure. 
About  a  minute  after  lighting  the  fuse,  the  workman  knocks  the 
stopper  out  of  the  bottom  of  the  crucible,  and  the  white-hot  metal 
pours  out  into  the  mould.  As  the  stream  enters  the  mold  from 
below  (Fig.  71)  it  heats  the  ends  of  the  rails  and  passes  on  up  and 
out  into  the  riser.  The  last  of  the  metal  stream  remains  in  the 
mold,  and  as  it  is  very  much  hotter  than  the  melting  point  of  steel, 
it  eats  into  the  sides  of  the  rails  and  knits  fast  on  cooling.  The 
joint  should  remain  undisturbed  for  at  least  five  minutes  to  allow 
the  metal  to  harden.  It  may  then  be  treated  in  a  number  of 
ways — either  allowed  to  cool  slowly  in  the  mold,  in  which  case 
the  joint  will  be  composed  of  soft,  tough  steel,  or  quenched  in  oil 
from  a  red  heat,  in  which  case  the  joint  will  be  very  hard,  and  per- 
haps brittle. 

While  this  description  does  not  give  all  of  the  steps  of  rail 
welding,  it  will  give  the  reader  a  fair  idea  of  how  all  thermit 
welds  are  made.  The  apparatus  used  is  as  follows : 

The  Crucible. — With  the  exception  of  butt-welding,  where  an 
ordinary  hot  crucible  is  used,  the  crucible  for  all  thermit- welding 


126 


WELDING 


is  a  cone-shaped  affair  that  taps  at  the  bottom.  It  is  an  evolution 
of  the  thermit  process,  and  is  so  designed  that  the  molten  iron  can 
be  drawn  off  before  the  slag  (Fig.  65). 

It  is  in  the  shape  of  an  inverted  cone,  having  a  rounded  iron 
top  which  is  clapped  on  as  soon  as  the  charge  is  fired  to  prevent 
spattering  and  loss  of  heat.  The  crucible  is  tapped  through  a 
hole  in  the  bottom.  It  is  supported  on  a  tripod  or  can  be  slung 
from  a  crane  or  overhead  arm. 

The  body  is  of  pressed  steel,  lined  with  several  inches  of 
magnesia.  Magnesia  is  slightly  more  refractory  than  silica  and 
it  has  the  advantage  that  it  will  not  unite  so  readily  with  the 
molten  steel.  Hence  the  steel  remains  basic. 


Removable  Top 


Asbestos  Washer 
Sand 


Tap  Hole 


Magnesia 
"Lining 

Iron 
Casing 


(Tapping  Pin 


Magnesia. 
Stone 

Magnesia 
Tnimble 


-Tapping  Ein, 


FIG.  65. — Thermit  crucible  with  detail  of  lap  hole. 

The  tap  hole  is  the  vital  part  of  the  crucible.  It  must  remain 
fluid-tight  until  tapped,  and  must  then  withstand  the  rush  of 
molten  steel  under  pressure.  As  shown  in  figure  65,  the  bottom 
of  the  crucible  holds  a  large  cylindrical  magnesia  stone  which  has 
been  placed  in  position  before  the  magnesia  lining  has  been 
tamped  in.  Resting  inside  the  stone  is  another  conical-shaped 
magnesia  stone,  called  the  "thimble."  It  is  also  hollow,  and  its 
core  is  the  channel  for  the  molten  steel.  An  iron  tapping  pin, 
haying  a  long  shank  and  a  flat  head,  is  dropped  into  the  hole  in 
the  thimble;  its  head  acts  as  a  plug  to  the  channel.  An  asbestos 
washer  is  dropped  on  the  head  of  the  tapping  pin,  then  an  iron 
washer,  and  next  an  inch  of  silica  sand  is  poured  on  the  iron 
washer.  This  makes  a  plug  to  the  crucible  that  is  fluid-tight  for 
at  least  a  minute,  long  enough  for  the  reaction  to  take  place. 


THE    THERMIT   PROCESS 


127 


This  plug  is  tapped  by  driving  the  pin  up  from  the  outside  by 
hitting  it  with  a  spade.  The  fluid  rushes  out  and  melts  the 
tapping  pin  as  it  goes. 

A  new  tapping  pin  is  needed  with  each  reaction;  a  new  thimble 


FIG.  66. — Rail  patterns. 

every  eight  or  ten  reactions;  a  new  crucible  lining  every  twenty  to 
more  reactions. 

The  lining  of  the  crucible  is  a  mixture  of  tar  and  magnesia, 
which  is  tamped  in  between  the  crucible  steel  and  an  iron  matrix. 
When  lined,  the  crucible  is  baked  at  a  red  heat  for  six  hours, 
when  the  lining  becomes  hard.  Even  such  a  substance  as  mag- 


FIG.  67. — Rail  mold  boxes. 

nesia  melts  away  under  the  heat  of  the  thermit  reaction,  and  after 
several  melts  the  interior  resembles  the  walls  of  a  Bessemer 
crucible. 

The  Mold.—  Molds  for  thermit  work  are  adapted  to  the  par- 
ticular joint  to  be  made.     For  welding  a  number  of  joints  of  uni- 


128  WELDING 

form  size  the  company  furnishes  patterns  with  which  the  operator 
can  make  his  own  molds,  or  else  the  company  will  furnish  the 
molds  themselves.  Thus  it  will  be  convenient  and  cheap  to  buy 
or  make  special  molds  for  continuous  rail  welding,  pipe  welding, 
rod  welding  (as  in  the  case  of  steel  rods  in  reinforced  concrete), 
locomotive-frame  welding,  or  in  other  repair  work  that  turns  up 
regularly. 

Take  the  case  of  rail  welding,  such  as  the  welding  together  of 
a  continuous  third  rail  for  the  Paris,  France,  subway.  We  will 
presume  the  mold  patterns  (Fig.  66)  to  represent  the  obverse 
shape  of  the  rail.  The  patterns  are  laid  down,  face  upward, 


Head 


Base  -* 


FIG.  68. — Finished  rail  molds. 


and  covered  with  their  respective  mold  boxes  (Fig.  67).  The 
molding  material  is  then  rammed  into  place,  and  when  the  box 
is  level-full,  the  operator  pricks  a  number  of  holes  all  the  way 
through  the  mold  to  allow  the  escape  of  gases  when  the  mold  is  in 
use.  As  soon  as  formed  the  molds  are  placed  in  a  drying  oven 
for  six  hours  at  a  heat  of  500  deg.  Fahr.,  until  they  have  become  a 
light  brown  color.  Do  not  let  them  burn  black,  as  they  will  then 
crumble  easily.  The  molds  are  generally  cast  inside  of  an  iron 
retaining  frame  or  with  iron  handles. 

Mold  sand  must  be  more  refractory  than  the  ordinary  river 
sand,  which  has  enough  iron  and  alumina  in  its  make-up  to 
render  it  easily  fusible  by  the  hot  thermit.  Coarse  white  silica 
sand  and  fire  clay  in  equal  proportions  is  the  best,  price  consid- 
ered. Cheap  rye  or  wheat  flour,  proportion  of  i  to  15,  is  the 
binder  used.  The  sand  and  flour  are  mixed  dry  and  then  mois- 
tened to  a  stiff  mass.  Where  an  extra  strong  mold  is  needed,  the 


THE    THERMIT    PROCESS 


I2Q 


operator  can  mix  a  spoonful  of  turpentine  to  each  mold  portion. 
For  binding  material  it  is  not  advisable  to  use  the  foundryman's 
occasional  expedients,  such  as  molasses,  larger  amounts  of 
flour,  clay,  pitch,  etc.,  for  two  reasons:  The  binder  is  subject 
to  the  great  heat  of  the  molten  thermit.  The  more  binder  used, 
the  greater  space  will  be  left  when  it  burns  out,  and  the  mold  will 


FIG.  69.— Mold  partially  assembled. 

fall  to  pieces  after  two  or  three  usings.  Also,  if  much  binder  is 
used,  its  rapid  burning  will  cause  excessive  gases  which  may 
burst  the  mold,  and  which  are  also  liable  to  injure  the  composition 
of  the  steel  joint. - 

A  good  sand-flour  mold  should  last  for  ten  or  more  welds. 
Its  life  depends  on  the  operator's  skill  in  making  and  his  care  in 
using  it. 


Pouring 
Gate 


Riser 


Opening 
or  Frame 


FIG.  70. — Assembled  thermit  mold. 

For  the  welding  of  joints  similar  to  rails,  the  molds  used  will 
vary  in  shape,  but  have  the  same  composition.  The  operator 
can  carve  his  own  patterns  out  of  wood. 

For  butt-welding  of  pipes  not  exceeding  a  diameter  of  i  1/2 
inches  and  of  solid  rods  not  exceeding  4  square  inches  cross- 
9 


I30 


WELDING 


section,  an  iron  mold  is  preferable  because  it  is  solid  and  easy  to 
handle  (see  Fig.  75). 

For  welding  larger  breaks,  such  as  fractured  locomotive  frames, 
the  fire-clay,  or  fire-brick,  mold  is  recommended.  In  this  case 
the  cross-section  to  be  welded  may  range  from  2  by  3  to  5  by  6 


Riser. 


v         /Pouring  Gate 


\Heating  Gate 

FIG.  71. — Sectional  view  of  mold. 

inches.  An  iron  mold  would  absorb  the  heat  too  rapidly.  The 
thermit  collar  would  chill  prematurely,  and  the  mold  itself  would 
probably  crack  or  melt,  being  cast  iron.  While  a  soft  sand  mold 
would  propably  crumble.  The  company  furnishes  a  hard- 
baked,  fire-brick  mold,  which  is  strong  and  refractory,  at  the 
same  time  being  a  fair  non-conductor  (Figs.  69  and  70). 


FIG.  72. — Tapping  the  crucible. 

It  often  happens,  in  thermit  repair  work,  that  the  fracture  to  be 
mended  is  of  a  peculiar  shape.  The  operator  will  be  at  a  disad- 
vantage in  making  his  patterns,  as  the  fracture  is  not  only  irre- 
gular, but  the  shape  of  the  piece  prevents  measurements  for  a 
mold  being  taken,  In  this  case  the  operator  builds  up  a  collar 


THE    THERMIT   PROCESS  131 

of  cerecine  wax  of  the  size  and  shape  that  he  intends  for  the 
finished  welded  collar.  He  then  places  the  piece  in  an  iron  mold 
box,  and  tamps  it  around  with  wet  sand,  at  the  same  time  insert- 
ing wooden  forms  for  pouring  gate  and  riser;  he  next  turns  the 
flame  of  a  gasoline  torch  into  a  special  hole  in  the  bottom  of  the 
sand  box.  The  wax  melts  from  around  the  piece  and  runs  out  of 
the  hole.  The  flame  is  continued  until  the  sand  is  dried, 
and  then  the  operator  stops  the  bottom  hole  in  the  mold 
with  a  sand  plug.  As  already  suggested  the  amount  of  ther- 
mit powder  necessary  for  such  a  mold  is  thirty-two  times  the 
amount  of  wax,  by  weight.  It  should  take  less  than  twenty 
minutes  to  place  a  wax  collar  on  an  ordinary  break  and  twenty 
minutes  to  dry  out  the  mold.  The  cost  of  the  wax  is  about  ten 
cents  per  pound,  so  that  for  mending  occasional  or  oddly-shaped 
breaks  the  wax  mold  is  the  cheapest  and  quickest.  It  is  used  for 
welds  of  embossing-  and  stamping-press  pieces,  forging  hammers, 
stern-posts  and  rudder-posts  of  sailing  vessels,  gun-carriages, 
motor  cases,  etc.,  etc. 

Practice. — It  should  be  borne  in  mind  that  the  thermit  joint 
itself  is  a  steel  casting  of  average  analysis  of : 

Carbon 0.05  to  o.  10 

Manganese 08  to     .10 

Silicon 09  to     .20 

Sulphur 03  to     .04 

Phosphorus 04  to     .05 

Aluminium 07  to     .18 

Its  average  tensile  strength  is  about  30  tons  per  square 
inch  cross-section.  If  the  joint  is  good,  the  thermit  will  amalga- 
mate so  closely  with  the  metal  of  the  welded  parts  that  a  ground 
and  polished  section  of  the  joint  will  not  show  any  marks  of 
junction,  even  though  the  metals  be  of  different  color  and  struc- 
ture. Therefore,  the  operator  has  only  to  calculate  whether  he 
shall  vary  the  chemical  composition  of  his  thermit  to  give  his 
weld  the  desired  strength  or  whether  he  should  gain  strength 
by  casting  a  big  shoulder  on  the  joint. 

There  are  a  number  of  instances  where  the  shoulder  must  be 
machined  off,  though  the  weld  must  be  as  strong  as  the  rest  of  the 
piece,  as  in  the  case  of  rails,  bearings,  etc. 


132  WELDING 

Most  welds  permit  of  as  large  a  shoulder  as  is  needed,  as 
in  the  case  of  ship  stern-posts. 

To  make  sure  that  the  metal  of  the  shoulder  adheres  to  the 
parts,  the  latter  should  be  made  hot  before  the  thermit  is  poured. 
If  the  shoulder  is  simply  a  loose  collar  of  metal  around  the  part, 
it  does  not  add  to  the  strength  of  the  weld.  Where  the  welded 
part  is  subject  to  bending  stresses,  it  is  important  that  the  shoul- 
der be  knit  to  the  surface  of  the  parts  welded.  The  company 
recommends  heating  the  parts  to  redness  if  possible  before  pouring 
the  thermit. 


ffw^iaa*! 


FIG.  73. — Reproduction  of  photograph  of  a  weld  showing  "blow"  holes. 

It  is  claimed  that  the  air  holes  and  shrinkage  cavities,  which 
thermit  steel  sometimes  shows,  are  also  due  to  insufficient  heating 
(see  Fig.  73).  Where  the  parts  to  be  welded  are  quite  cold,  it  is 
probable  that  the  thermit  steel  freezes  as  soon  as  it  touches,  caus- 
ing imperfect  circulation  around  the  joint,  and  hence  allowing  a 
faulty  structure  in  the  weld. 

Blow  holes  and  separation  planes  are  two  of  the  common 
diseases  of  the  thermit  weld.  Faulty  mixing  of  the  thermit 
"tonics,"  improper  preheating,  and  improper  pouring  or  tapping 
are  all  blamed  for  these  defects. 

Setting  the  Pieces. — Where  two  pieces  of  iron  of  more  than 
i-inch  section  are  to  be  joined,  it  is  best  to  allow  a  1/2  inch  space 
between  the  abutting  ends,  for  it  is  necessary  that  the  thermit 


THE    THERMIT    PROCESS  133 

have  free  flow  around  the  ends.  It  must  either  melt  the  abutting 
ends  or  there  must  be  a  passage  between  them  for  the  thermit 
to  flow. 

In  the  case  of  rails,  the  ends  of  the  rails  are  brought  close 
together,  as  the  thermit  can  easily  melt  the  ends.  The  same 
is  also  true  in  the  case  of  small  rods  and  pipe.  It  is  important 
to  keep  the  rails  in  perfect  alignment  while  welding. 

In  the  case  of  locomotive  frames  where  it  is  doubtful  whether 
the  thermit  could  melt  its  way  into  the  fracture,  the  operator 
drills  a  line  of  i/2-inch  holes  down  the  break;  through  these 
holes  the  thermit  enters  (see  Fig.  85).  Also  in  the  case  of  anchor 
flukes,  ship's  stern-  and  rudder-posts,  large  castings,  such  as 
anvils,  hydraulic  hammers  and  presses,  etc. 

In  the  case  of  locomotive  frames  and  driving-wheel  spokes 
the  shrinkage  of  the  joint  on  cooling  will  spoil  the  piece  if  not 
allowed  for.  The  locomotive  frame  is  jacked  open  from  1/8 
to  i/i 6  inch  before  the  mold  is  placed.  In  the  case  of  the  driv- 
ing-rod equal  expansion  of  the  other  spokes  on  the  piece  can  be 
had  by  heating  short  sections  of  each  spoke  to  redness  until  the 
weld  around  the  broken  spoke  begins  to  set.  All  the  spokes  will 
contract  together  and  the  strain  will  be  minimized. 

Cleaning  the  Pieces. — The  thermit  reaction  consists  in  the 
reducing  of  iron  oxid  by  aluminum.  Hence  it  is  supposed  that 
the  thermit  steel,  when  molten,  will  clean  the  scale  off  the  joint 
to  be  welded.  So  it  will;  but  this  scale  will  go  into  solution 
as  iron  oxid.  If  there  is  much  scale  on  the  joint,  the  thermit 
joint  will  become  full  of  iron  oxid  and  will  be  "burnt"  and 
brittle.  Contrary  to  the  advise  contained  in  the  company's 
directions,  I  would  recommend  that  the  pieces  be  kept  as  clean 
of  scale  as  possible.  If  they  are  heated  to  redness  in  preheating, 
of  course  fresh  scale  will  be  formed.  But  the  operator  should 
begin  by  cleaning  his  pieces  with  sand  blast  or  sand-paper  or  by 
tapping. 

As  with  ordinary  blacksmith  welds,  it  is  also  important  to  rid 
the  joint  of  grease  by  mechanical  means  or  by  scouring  it  with 
dilute  alkali. 

Preheating. — It  is  necessary  to  heat  with  a  torch  all  pieces 
about  to  be  joined,  for  the  reason  that  the  molten  thermit  must 


134  WELDING 

meet  a  hot  responsive  surface  of  metal  when  it  flows  into  the 
mold.  If  poured  into  a  cold  mold  and  on  to  a  cold  joint,  the 
thermit  may  be  chilled  enough  to  make  it  flow  slowly  and  im- 
perfectly. The  result  will  be  an  imperfect  junction,  and  the 
shoulder  of  the  weld  may  be  full  of  air-holes  and  minute  cleavage 
planes  from  rapid  cooling.  Do  not  rely  on  the  great  heat  of 
thermit,  but  preheat  in  all  cases  except  butt-welding. 

For  most  work  a  gasoline  or  benzene  torch  is  good  enough. 
The  flame  is  fairly  neutral  and  will  not  form  scale  very  fast. 

For  heating  very  large  pieces,  several  torches  are  often  needed. 
In  shop  repairing,  producer  gas  may  be  used;  and  in  this  event 
the  burner  can  be  made  to  give  a  reducing  flame,  which  will 
prevent  scale  from  forming. 

As  to  temperature,  the  joint  should  be  at  least  hot  enough  to 
vaporize  water  drops  with  violence.  It  is  well  to  heat  the  joint 
to  redness  where  it  can  be  done.  But  where  the  pieces  are  large, 
they  will  conduct  the  heat  away  from  the  part  where  the  flame 
is  playing;  the  operator  must  be  satisfied  with  a  temperature 
ranging  about  300  deg.  Cent. 

Safe- guarding  the  Mold. — Bear  in  mind  that  liquid  thermit 
is  exceedingly  fluid — as  much  so  as  warm  molasses — and  as  it  is 
much  heavier,  it  will  search  diligently  for  all  openings  in  the  mold. 
For  this  reason  the  mold  must  be  tight  at  the  entering  of  the  iron 
pieces.  The  operator  should  have  at  hand  a  bucket  of  luting 
clay,  made  of  equal  mixtures  of  fire-clay  and  sand,  made  pasty 
with  a  little  water. 

If  the  molds  are  solid  pieces,  as  in  rail  and  locomotive-frame 
welding,  he  smears  a  thin  layer  over  the  surface  of  the  molds 
where  they  come  in  contact  with  one  another.  This  will  make  a 
fairly  tight  mold. 

Also  he  must  stuff  luting  clay  around  the  mold  where  the 
iron  pieces  enter,  otherwise  the  thermit  may  find  its  way 
along  the  iron  and  spurt  out.  The  danger  of  an  unexpected 
squirt  of  thermit  need  not  be  dwelt  on. 

When  the  mold  is  made  of  fire-clay  tamped  over  a  wax  collar, 
there  should  be  no  leaks  if  the  operator  is  careful.  He  must  be 
sure  that  his  mold  is  rigid  and  strong  enough  to  hold  the  extra 
weight  of  the  pour. 


THE    THERMIT   PROCESS  135 

A  possible  overflow  of  thermit  and  slag  must  be  provided  for. 
Large  pours  of  thermit  are  always  made  with  this  in  mind.  If 
the  pour  is  made  in  the  workshop,  the  floor  should  be  of  sand 
and  the  workman  should  remove  his  tools  before  tapping.  After 
tapping  the  thermit  he  should  remove  himself  as  quickly  as 
possible. 

Amount  of  Thermit. — As  has  been  stated  elsewhere,  there 
should  be  twice  as  much  thermit  steel  poured  for  a  weld  as  is 
necessary  to  fill  the  space  between  the  joined  pieces  and  to  provide 
for  shoulder  around  the  joint.  The  first  of  the  thermit  pour 
that  reaches  the  inside  of  the  joint  expends  most  of  its  heat  in 
raising  the  temperature  above  redness.  It  passes  up  the  riser, 
leaving  the  interior  so  hot  that  the  last  of  the  pour  settles  easily 
around  the  half-molten  joint  and  is  fluid  enough  to  make  a  homo- 
geneous casting. 

The  amount  of  the  thermit  powder  used  in  a  weld  is  eighteen 
times  the  unoccupied  space  in  the  mold  after  the  joint  is  adjusted 
and  ready  to  weld.  The  thermit  is  estimated  in  ounces,  the 
space  in  cubic  inches  (page  124).  This  number,  eighteen, 
provides  twice  as  much  thermit  steel  as  is  needed  for  the  weld, 
the  rest,  as  already  stated,  going  into  the  riser.  However,  P. 
Redington1  and  H.  L.  Des  Anges2  advise  that  three  or  even  four 
times  the  amount  of  steel  is  needed  to  get  the  best  results.  This 
may  be  due  to  imperfect  preheating. 

The  Reaction. — The  reaction  is  rapid  and  violent.  There 
is  no  explosion,  but  the  crucible  sends  up  a  shower  of  sparks  much 
like  the  kind  of  fireworks  called  a  "  flower-pot."  So  to  prevent 
this  and  to  conserve  the  heat,  a  loose  metal  top  is  slipped  over  the 
crucible  as  soon  as  the  fuse  is  lit. 

The  workman  should  use  smoked  or  colored  glasses  to  protect 
his  eyes. 

The  reaction  takes  not  longer  than  thirty  seconds.  The 
crucible  should  not  be  tapped  for  at  least  ten  seconds  thereafter, 
because  the  reaction  has  left  an  intimate  mixture  of  slag  in  steel 
in  the  crucible,  and  a  little  time  is  allowed  for  the  slag  to  float  to 
the  surface.3  I  believe  that  outside  of  insufficient  perheating,  one 

1  Foundry,  April,  1905. 

2  Foundry,  August,  1905 

3  Ibid.,  R.  Webb,  July,  1905. 


136  WELDING 

of  the  common  causes  of  failure  of  thermit  welds  is  premature 
tapping.  1  No  steel  is  strong  if  it  is  premeated  with  slag. 

After  Pouring.  —  After  pouring,  you  have  an  ordinary  steel 
casting,  with  this  exception  —  that  the  heat  of  the  joint  will  be 
conducted  by  the  body  of  the  part  much  faster  than  is  good  for  a 
steel  casting.  If  'you  are  welding  a  fractured  locomotive  frame, 
and  you  want  to  assure  yourself  that  the  joint  will  be  as  tough  as 
the  frame,  you  had  best  give  the  joint  several  hours'  annealing  by 
such  means  as  are  at  hand. 

Annealing  is  not  so  necessary  in  a  thermit  joint  as  it  is  in  the 
oxy-acetylene  and  other  welds.  Thermit  steel  shows  a  low- 
carbon  content.  Rapid  cooling  will  not  temper  it  highly.  But 
no  chilled  steel  is  as  tough  as  the  annealed  product.  Tests  in 
practice  seem  to  show  that  after-heating  gives  an  even-grained 
and  tougher  joint.2 

The  results  of  after-heating  may  be  attained  in  a  lesser  degree 
by  keeping  the  mold  in  place  until  the  joint  is  cooled.  Cooling 
may  take  several  hours  with  the  mold  on  if  the  pieces  are  large. 

Nickel  Addition.  —  Nickel  thermit  is  an  allied  substance  to 
thermit  proper.  It  is  a  mixture  of  nickel  oxid  and  aluminum,  and 
the  reaction  sets  free  the  nickel  in  the  metallic  state. 


If  the  operator  wants  a  higher  tensile  strength  without  dimin- 
ishing his  elastic  limit,  he  introduces  a  can  of  nickel  thermit 
into  his  ladle  of  molten  iron,  as  already  described.  Or  the 
nickel  thermit  is  fired  in  a  hand-ladle,  using  a  small  quantity,  and 
pouring  in  the  remainder  of  the  package  gradually  as  the  reaction 
progresses.  The  entire  contents  of  the  hand-ladle  are  poured 
into  the  big  ladle,  which  should  be  one-third  full  of  molten  iron. 
The  big  ladle  is  then  poured  full  of  iron  and  a  can  of  titanium 
thermit  is  poled  in  to  cause  a  thorough  mixing  of  the  iron  and 
nickel. 

One  per  cent,  of  nickel  is  sufficient  to  increase  the  strength  of 
ordinary  iron  about  one-third.  Two  per  cent,  of  nickel  thermit 
gives  a  little  more  than  i  per  cent,  metallic  nickel. 

1  Foundry,  Jas.  F.  Weber,  July,  1905. 

2  Journal  U.S.  Artillery,  Gustav  Reiniger,  July-August,  1907. 


THE  THERMIT  PROCESS  137 

Metallic  nickel  is  also  added  to  thermit,  using  5  ounces 
nickel  to  each  100  pounds  thermit  if  you  wish  to  make  a  i  per 
cent,  alloy. 

Titanium  Addition. — Titanium  thermit  is  another  "alumino- 
thermic"  substance  having  the  reaction 

3TiO2  +4A1  =  2  A12O3  +3!! 

It  is  introduced  into  the  ladle  in  foundry  practice  for  the 
purpose  of  purifying  the  iron.  About  i  per  cent,  is  recommended. 
As  its  office  is  to  reduce  the  sulphur  and  nitrogen,  most  of  it  re- 
appears in  the  slag.  Its  effect  is  to  greatly  increase  the  strength, 
presumably  by  making  the  metal  close-grained  and  homogeneous. 

Butt-welding  of  Pipes. — One  of  the  unique  applications  of 
thermit  is  in  the  butt-welding  of  pipes  and  bars.  It  is  a  very 
difficult  and  often  impossible  thing  to  make  a  strong  joint  of  two 
gas  or  water  pipes  without  cutting  reverse  threads  on  the  two 
and  using  a  sleeve  union.  Welding  such  joints  by  ordinary 
means  is  generally  out  of  the  question,  because  with  the  facilities 
ordinarily  at  hand,  it  is  difficult  to  obtain  the  right  welding  heat, 
and  almost  impossible  to  keep  the  surfaces  clean  enough  to  join 
them. 

In  using  thermit  for  butt- welding,  the  slag  of  the  thermit  reac- 
tion is  poured  into  the  mold  before  the  metal.  It  covers  the  iron 
surface  in  a  thin  layer  that  is  at  once  chilled  and  adheres  to  the 
metal.  This  coating  of  slag  serves  as  a  distributor  of  the  heat 
of  the  thermit  metal  to  the  iron,  at  the  same  time  preventing  direct 
contact  of  the  thermit  metal  with  the  pipe.  As  soon  as  the  oper- 
ator believes  the  pipe  ends  are  plastic,  he  pulls  them  tightly 
together,  and  the  weld  is  effected. 

As  this  is  a  very  practical  and  necessary  weld,  it  will  be  well  to 
explain  the  operation  and  the  appliances  in  detail. 

Suppose  two  i-inch  abutting  gas  pipes  are  to  be  welded.  The 
ends  are  first  cut  square  and  filed  to  smoothness,  so  that  when  the 
pipes  touch  their  ends  shall  fit  closely  all  around.  Clamps  are 
then  fitted  on  the  pieces,  about  5  inches  from  the  ends,  and 
screwed  tightly  on  the  pipes.  These  clamps  have  sockets  for 
two  connecting  draw  screws,  which  are  fitted  in  place  and 


'33 


WELDING 


tightened  with  pins  (see  Fig.  74)  until  the  pipe  ends  touch. 
Brace  the  pipes  so  that  they  align  as  they  should  and  place  the 
lower  mold  jaw  under  the  joined  ends  of  the  pipes,  so  that  the 
line  of  joining  is  in  the  middle  of  the  mold.  This  mold  is  a 
hinged  affair,  having  two  handles,  and  resembles  a  nut-cracker 
(see  Fig.  75). 


Draw  Pin 


Joint 


Draw  Pin 
FIG.  74. — Clamps  in  position.    Pipe-welding  by  thermit. 

The  thermit  portion,  about  2  pounds,  is  poured  into  a  small 
cup  crucible,  which  is  lined  with  magnesia  and  operated  with 
a  pair  of  tongs.  Allow  the  crucible  to  stand  half  a  minute  after 
firing,  so  that  the  slag  and  steel  can  separate.  Then  pour  over 
the  lip  of  the  crucible  so  that  the  slag  comes  out  first.  Begin 
pouring  at  one  end  of  the  lip  of  the  mold  and  travel  to  the  other 
end.  As  the  thermit  slag  is  poured  in  on  a  cold  surface  of  pipe, 


Pouring  Gate 


FIG.  75. — Mold  for  pipe- welding  with  thermit. 

it  forms  a  hard  shell  around  the  metal,  and  the  liquid  which 
follows  distributes  its  heat  evenly  through  this  shell,  which  is  a 
poor  conductor.  During  the  pouring,  the  operator's  assistant 
presses  the  handles  of  the  mold  together  to  keep  the  mold  in  close 
contact  with  the  pipe.  About  one  minute's  time  is  allowed  for 
the  iron  of  the  pipe  to  reach  welding  heat.  The  draw  pins  are 


THE    THERMIT   PROCESS 


139 


Pouring 
Gate 


put  in  the  sockets  of  the  clamps  and  screwed  tight.  If  the  pipe 
ends  are  plastic  and  ready  to  weld,  the  operator  can  feel  it  by 
screwing  the  draw  pins.  The  nuts  on  both  pins  are  given  two 
full  simultaneous  turns  by  the  operator  and  his  assistant.  This 
is  enough  to  force  the  pipe  ends  together  and  complete  the  weld. 
If  the  operator  desires,  he  can  force  enough  metal  into  the  upset 
by  giving  the  draw  nuts  another  turn,  to  make  the  joint  con- 
siderably stronger  than  the  pipe  itself. 

Thje  mold  is  taken  off  at  once  by  tapping  the  upper  jaw  loose 
with  a  hammer.  The  slag  collar  which  adheres  to  the  pipe  is 
knocked  off  carefully,  and  the  red-hot  joint 
is  allowed  to  cool. 

The  draw  bars  and  clamps  which  held 
the  pipes  together  are  removed  as  soon  as 
the  weld  is  cooled.  The  joint  will  have  a 
slight  upset  due  to  the  extra  metal  forced 
into  it.  This  may  be  machined  off  if 
necessary. 

Tests  on  such  a  weld  will  give  a  frac- 
ture or  a  crease  in  the  pipe  outside  of  the 
line  where  the  mold  fitted. 

The  foregoing  weld  was  made  on  a  hori- 
zontal piece  of  piping.  For  an  inclined  or 
vertical  piece,  the  apparatus  and  process 
are  the  same,  except  that  the  mold  will 
have  its  mouth  placed  in  the  side  so  that  the  thermit  can  be 
poured  in  when  the  mold  is  in  place  (see  Fig.  76). 

For  pipes  or  rods  of  different  thickness  or  diameter,  the  size 
of  the  mold  will  vary,  also  the  amount  of  thermit  to  use  and  the 
time  it  takes  to  raise  the  joint  to  welding  heat.  The  manufac- 
turers supply  both  molds  and  clamps  for  pipes  and  rods  of 
standard  sizes,  and  specify  the  amount  of  thermit  to  use  in  each 
case. 

In  this  application  of  thermit,  it  should  be  noted  that  the 
thermit  steel  does  not  come  in  contact  with  the  pieces  to  be  welded, 
nor  does  its  substance  form  a  part  of  the  weld.  Accordingly, 
thermit  butt-welding  is  applicable  to  pipes  and  rods  of  wrought 
iron  and  mild  steel,  and  not  to  cast  iron  and  high-carbon  steel. 


FIG.  76. — Clamps  and 
mold  in  place  for  weld- 
ing vertical  pipe. 


140  WELDING 

This  process  can  be  used  for  welding  gas  and  water  pipes 
while  in  the  ground;  steam  and  ammonia  and  compressed-air 
pipes;  pipe  coils,  before  or  after  bending;  steel  rods  in  reinforced 
concrete. 

The  entire  cost  of  making  one  weld  for  a  pipe  of  i-inch  bore 
is  approximately  $22.  This  includes  the  total  cost  of  the  appa- 
ratus necessary,  and  the  time  charge  of  one  hour  at  thirty 
cents  for  the  operator  and  twenty  cents  for  the  helper.  This 
prohibitive  cost  is  rapidly  reduced  for  welds  in  number,  just  as 
the  cost  of  a  printed  page  rapidly  decreases  as  the  number  printed 
increases.  One  hundred  welds  like  the  above  would  cost,  ap- 
proximately, one  dollar  each,  supposing  that  two  welds  could 
be  made  per  hour.  The  first  cost  of  tongs  and  clamps  is  final, 
while  the  crucible  must  be  replaced  after  about  ten  firings  and 
the  mold  after  fifty  welds.  The  cost  of  the  thermit  and  the 
ignition  powder  and  also  the  labor  is  a  constant. 

One  of  the  rivals  to  this  welded  joint  is  the  plumber's  sleeve 
joint.  In  comparing  the  two  methods  of  joining,  the  contractor 
must  consider  several  things;  will  it  be  cheaper  to  cut  a  thread 
on  each  pipe  end  and  sleeve  the  joint?  Also,  will  it  be  possible 
for  the  workman  to  get  at  his  joint  to  cut  the  thread  ?  Is  a  leak 
at  the  joint  going  to  be  a  vital  matter?  A  weld  cannot  leak, 
while  any  other  joint  is  apt  to  under  pressure,  especially  where 
the  pipes  are  cold,  as  in  ammonia  plants.  Will  a  sleeve  joint 
be  strong  enough  in  cases  where  the  pipes  are  subject  to  strain  ? 
And,  finally,  how  do  the  total  costs  compare?  This  last  will 
depend  largely  on  the  number  of  joints  to  be  made. 

Another  rival  is  the  oxy-acetylene-blowpipe  weld.  It  is 
probable  that  with  this  method  one  workman  can  make  from 
one  to  four  welds  an  hour,  depending  on  the  amount  of  labor 
he  must  put  on  cutting  and  fitting  the  pipe  ends  preparatory  to 
welding.  This,  together  with  the  cheapness  of  the  gas  used, 
makes  the  operating  cost  much  less  than  the  thermit  butt- weld. 
However,  the  cost  of  the  apparatus,  two-  gas  storage  tanks,  the 
blowpipe,  and  the  checks-valves  is  much  greater.  Also,  to 
travel  from  pipe  to  pipe,  often  necessary,  the  operator  would  need 
an  assistant  to  carry  the  heavy  tanks,  etc. 

Butt-welding  of  pipes  can  be  done  by  the  Thomson  electric 


THE    THERMIT    PROCESS  141 

process.  But  this  process  is  at  a  disadvantage  here  because  the 
welding  must  be  carried  on  in  a  heavy  machine.  Whereas, 
when  pipes  are  to  be  butt-welded,  the  chances  are  that  they  are 
in  some  out-of-the-way  corner  of  a  room  or  cellar  and  cannot  be 
taken  out. 

Mending  Defective  Castings. — Besides  its  use  in  welding, 
thermit  is  being  exploited  for  the  repair  of  defective  castings, 
which  is  not  strictly  a  welding  operation.  Also  for  raising  the 
temperature  of  the  ladle  before  pouring  for  castings;  for  poling 
"burnt  iron";  for  the  introduction  of  nickel,  titanium,  etc.,  into 
molten  iron;  for  the  formation  of  alloys;  for  the  reduction  of  the 
less  common  metals  from  the  refractory  ores  and  earths.  Though 
these  last  have  nothing  in  common  with  welding,  they  will  be 
treated  of  briefly,  so  that  the  treatise  on  thermit  may  be 
complete. 

In  the  foundry,  in  the  casting  of  large  and  expensive  pieces, 
the  loss  by  defective  castings  is  sometimes  equal  to  the  price 
asked  for  the  casting,  due  to  cracks,  bad  flows,  breaks,  and  inop- 
portune blow  holes.  If  the  foundryman  can  save  such  pieces 
from  the  melting  pot,  he  will  greatly  increase  his  profits. 

For  mending  small  surface  defects,  where  the  idea  is  to  replace 
the  surface  without  regard  to  the  strength  of  the  patch  made, 
the  following  method  is  advised.  First,  chip  out  the  defect  to 
be  sure  that  it  is  superficial.  Heat  the  casting  around  the  hole  to 
a  red  heat.  Then  bank  a  basin  of  sand  around  the  hole.  Place 
a  piece  of  abestos  in  the  bottom  of  the  basin,  large  enough  to 
cover  the  hole.  Pour  thermit  powder  into  the  basin,  using  18 
ounces  of  thermit  for  every  cubic  inch  estimated  space  of  hole 
in  the  metal.  If  the  casting  is  a  large  one,  use  a  greater  per- 
centage of  thermit,  as  more  heat  will  be  needed.  Fire  the  thermit, 
and  it  will  quickly  melt  the  asbestos  bottom,  and  the  molten  steel 
will  be  deposited  in  the  hole  in  the  metal.  When  cool,  the  pro- 
truding metal  is  machined  off. 

This  reaction  is  too  rapid  for  the  complete  separation  of  the 
slag,  some  of  which  may  be  lodged  on  the  junction  of  the  thermit 
metal  and  the  casting.  Also,  it  is  likely  that  the  local  heating 
will  cause  weakening  stresses  in  the  patch  when  it  cools;  while 
it  may  also  be  full  of  blow  holes  if  it  cools  rapidly,  because  of 


142 


WELDING 


conduction.     It  is  claimed1  that  the  shrinkage  is  so  great  that 
such  a  repair  is  unsafe  and  useless. 

Thermit  may  be  used  for  repairing  fractures  in  castings  before 
they  leave  the  foundry.     If  the  casting  have  a  piece  broken  cleanly 


FIG.  77. — Thermit  can  plunged  into  ladle. 

off,  this  may  be  joined  at  a  less  cost  than  the  cost  of  recasting. 
Also  cracks  may  be  drilled  out  and  thermit  used. 

Thermit  in  Foundry  Practice. — Thermit  may  be  intro- 
duced into  the  ladle  before  pouring  for  a  casting.  If  the  piece 
to  be  cast  is  long  and  thin,  or  if  it  has  intricate  parts  which  require 
a  very  hot  metal  to  produce,  the  temperature  of 
the  iron  in  the  ladle  can  be  raised  by  plunging  a 
can  of  thermit  into  it  and  holding  it  at  the  bottom 
until  both  thermit  and  can  have  burned  up  and  the 
slag  has  come  to  the  surface.  The  excess  heat  of 
the  thermit  will  raise  the  temperature  of  the  ladle 
(Fig.  77). 

How  much  thermit  to  use  for  a  given  amount 

.       . _ 

tail  of  thermit  of  iron  cannot  be  stated  definitely — probably  5  per 
plunger  can.  cent  ^  depends  on  the  j^^  temperature  of 

the  ladle,  the  demand  of  the  casting,  and  the  cost.  The  cost 
prohibits  its  use  except  for  special  work,  such  as  the  casting  of 
stern-posts  for  ships,  and  the  production  of  small  castings  which 
can  be  made  at  any  time  without  the  capital  investment  for  a 
special  converter  plant. 

1  "Mending  a  Casting  with  Thermit,"  Pat  Redington,  Foundry,  April,  1905. 


THE    THERMIT    PROCESS  143 

The  company  also  recommends  placing  a  can  of  thermit  in 
the  riser  of  such  a  casting  as  a  ship's  stern-post.  If  the  post  is  to 
be  a  long  one,  "the  metal  cools  very  rapidly  during  its  passage 
through  the  mold,  and  becomes  so  sluggish  that  the  pressure  of 
the  runner  is  not  sufficient  to  force  the  metal  up  the  rising  heads 
more  than  one-half  of  their  length."  The  thermit  can  will 
reinforce  the  heat  of  the  rising  metal. 

To  prevent  "piping"  of  steel  ingots,  a  can  of  thermit  may  be 
plunged  into  the  ingot.  The  operator  waits  until  the  ingot  has 


FIG.  79. 


FIG.  80. 


FIG.  81. 


FIG.  79. — Steel  ingot  showing  defective  head  piping  without  anti-piping  thermit. 

FIG.  80. — Showing  ingot  with  box  of  anti-piping  thermit  in  position. 

FIG.  81. — Ten-ton  steel  ingot  having  been  treated  with  anti-piping  thermit. 

begun  to  solidify.  The  "  pipe  "  will  then  begin  to  form,  due  to  the 
chilling  of  the  steel  on  the  outside  and  its  contraction.  Break 
through  the  top  crust,  and  thrust  the  can  well  down  into  the  ingot. 
It  will  ignite  and  raise  the  temperature  of  the  upper  part  of  the 
ingot  to  remelting.  A  solid  ingot  will  result  (Figs.  79  to  81). 
This  is  another  use  for  thermit,  questionable,  because  of  its  cost. 
Poling. — As  has  been  described,  the  foundryman  often 
freshens  his  "burnt  iron,"  by  stirring  the  ladle  with  a  green  stick 
of  wood.  "Burnt  iron"  contains  oxygen  in  the  form  Fe2O3. 
This  oxid  of  iron  impairs  the  strength  of  the  iron  very  much. 


144  WELDING 

By  stirring  the  molten  mass  with  a   green  limb,  the  workman 
has  added  carbon  which  reduces  the  iron  oxid,  as  follows: 


The  limb  being  full  of  water  also  throws  out  steam  which 
causes  the  iron  to  boil.  This  makes  the  reaction  complete  through- 
out the  mass.  When  the  oxid  is  all  reduced,  the  ladle  is  "  fresh." 
But  this  operation,  called  "poling,"  lowers  the  temperature. 
Now  "poling"  can  be  done  with  a  thermit  can  on  the  end  of  a 
rod  instead  of  with  a  green  limb.  The  composition  of  the 
thermit  must  be  varied  so  as  to  have  a  positive  effect  on  the  oxid 
of  iron;  that  is,  there  must  be  a  slight  excess  of  aluminum. 
Thermit  "poling"  has  the  advantage  that  it  raises  the  tempera- 
ture of  the  molten  iron.  But  it  should  not  be  used  except  in  la- 
dles of  steel,  because  at  the  heat  of  molten  steel  there  is  complete 
reaction  with  the  excess  aluminum  in  the  thermit.  While  at  the 
lower  temperature  of  molten  cast  iron,  the  reaction  would  be 
confined  to  the  thermit  can.  The  excess  of  aluminum  would 
not  react  on  the  iron  oxid  of  the  burnt  mass,  and  both  would  stay 
in  solution.  In  other  words,  the  iron  would  be  poorer  than  ever. 

A  better  method  recommended  by  the  company  is  the  use  of 
manganese  with  the  thermit,  though  no  doubt  the  thermit  can  be 
omitted  if  we  do  not  wish  to  raise  the  temperature.  Pure  man- 
ganese, made  "  thermochemically,  "  can  be  used.  Manganese,  in 
the  form  of  ferro-manganese  and  spiegel,  have  long  been  known 
to  furnace  men  as  a  cure  for  "burnt  iron"  and  a  toughener  of 
their  product. 

W.  M.  Carr1  is  authority  for  the  statement  that  a  large  ladle 
can  be  used  for  a  small  converter  if  thermit  be  added  to  the  first 
pour  in  the  ladle  immediately  preceeding  the  second  pour.  The 
ladle  held  5  tons,  the  converter  2  tons,  the  pours  were  forty-five 
minutes  apart.  The  thermit  was  poled  into  the  first  pour,  as 
usual,  in  a  can  on  a  rod.  It  freshened  the  iron  and  raised  its 
temperature  to  about  that  of  the  second  pour. 

Adaptability.  —  In  summing  up  the  thermit  process  as  a  whole 
it  will  appear  that  it  is  especially  suited  for  welding  and  repair- 

1  "  Development  of  the  Thermit  Process  in  Foundry  Practice,"  Foundry, 
July,  1906. 


THE    THERMIT    PROCESS  145 

ing  large  pieces.  In  pieces  ranging  below  4  square  inches  cross- 
section,  it  has  to  meet  competition  with  theoxy-acetylene,  oxy-gas, 
oxy-hydrogen,  electric,  and  smithing  processes.  Its  application 
to  butt-welding  is  very  often  the  cheapest,  handiest,  and  most 
workmanlike. 

In  rail  welding  it  has  to  compete  with  the  electric  process, 
which  was  the  pioneer  in  this  field. 

In  welding  motor  cases  for  steel  cars  it  has  to  compete  with 
the  oxy-actylene  process. 


FIG.  82. — Fracture  on  locomotive  frame,  opened  up  by  drilling  and  held  in  place 
by  jacks  in  preparation  for  thermit  welding. 


In  welding  fractured  locomotive  frames  it  is  used  with  success, 
and  is  evidently  as  cheap  as  can  be  had — certainly,  much  cheaper 
than  the  old  blacksmithing,  for  the  weld  may  be  effected  often 
without  dismantling.  It  is  used  in  their  repair  shops  by  many 
of  the  railroads  in  this  country  and  abroad  for  repairing  engine 
frames  and  also  driving  rods  and  spokes,  and  occasionally  the 
repair  machinery.  The  Central  Railroad  of  New  Jersey  first 
introduced  thermit  in  their  shops. 

10 


146  WELDING 

It  is  used  for  occasional  repairs  of  fractured  gun-carriages  and 
parts. 

Also  for  crank  shafts,  embossing  dies,  shears,  and  anvils,  in 
cases. where  it  is  cheaper  to  repair  than  to  replace. 

For  broken  rudder  and  propeller  shafts,  skegs,  and  stern-posts 
of  vessels  it  is  invaluable.  This  is  the  most  notable  feature  of 
the  process.  Before  the  advent  of  thermit,  a  break  in  one  of 
the  parts  named  meant  the  dry-docking  of  the  vessel  for  weeks, 
the  displacing  of  the  part  broken  and  its  repairing  at  great 
expense  and  trouble,  or  sometimes  its  displacement.  Besides 
the  actual  expense  entailed,  much  was  lost  by  having  the  boat 
out  of  commission. 

Since  the  use  of  thermit  for  such  repairs,  dry-docking  is  still 
necessary,  but  the  whole  operation  can  be  gone  through  with  in 
much  less  than  a  week;  the  vessel  is  not  dismembered  and  the 
weld  may  be  made  the  strongest  part  of  the  piece.  Broken 
anchors  can  be  mended  in  a  few  hours.  As  already  described, 
there  are  many  instances  of  such  quick,  cheap,  and  strong  welds. 

Thermit  is  almost  a  new  subject.  It  has  been  known  to  the 
repair  men  since  about  1904.  It  is  already  a  definite  success,  and 
under  the  energetic  experimentation  of  the  Goldschmidt  Co.  it 
is  likely  to  prove  useful  in  ways  at  present  unthought  of.  It  is 
likely  that  special  thermits  will  soon  be  invented  for  welding  other 
metals  than  iron  and  steel. 

Typical  Welds. — In  the  welding  of  rail  joints  in  quantity 
there  are  a  number  of  large  contracts  that  have  come  to  notice. 
Among  them  the  joining  of  the  third  rail  of  the  Paris  subway;  the 
welding  of  10,000  joints  of  the  Electric  Traction  Company  of  Ade- 
laide, Australia;  the  welding  of  the  Lexington  Avenue  line  in  New 
York  City.  The  latter  was  especially  difficult  because  of  the  heavy 
traffic.  It  was  impossible  to  do  the  job  by  daylight  without 
tying  up  the  traffic.  In  the  early  morning  hours,  when  the  cars 
run  on  a  ten-minute  schedule,  the  company  succeeded  in  carrying 
on  their  welding  with  only  the  occasional  holding  up  of  a  car. 

The  cost  of  thermit  rail  welding  has  been  variously  estimated. 
Track  at  Holyoke,1  Mass.,  welded  in  1904,  cost  $6.23  per  joint. 
The  longest  unit  rail  made  was  2300  feet.  In  the  same  year  rail 

1  Street  Railway  Journal,  Feb.  18,  1905. 


THE    THERMIT   PROCESS  147 

welding  at  Hartford,1  Conn.,  cost  $5.00  per  joint,  which  figure 
includes  repaying. 

Among  pipe-welding  contracts,  that  carried  out  for  the  Man- 
hattan Refrigerating  Co.,2  of  New  York  City,  is  noteworthy. 
Their  entire  system  of  piping  was  welded  by  the  thermit  process. 
There  were  twenty-nine  i  i/4-inch  joints,  and  twenty-seven 
2-inch  joints,  both  under  a  cold  pressure  of  180  pounds.  The 
result  is  reported  as  successful.  This  is  a  decided  improvement 
on  the  sleeve  joint  for  ammonia  systems,  because  the  contraction 
of  the  pipes  due  to  the  extreme  cold  is  certain  to  allow  leakage  in 
the  sleeve  joint. 

Repair  of  the  "Betsy  Ann"5 

"  One  of  the  quickest  repairs  on  record  was  accomplished  on 
the  Mississippi  River  Steamship  '  Betsy  Ann/  belonging  to 
Learned  &  Son,  Natchez,  Miss.  This  is  a  stern  wheel  boat,  the 
shaft  being  a  hexagonal  one,  83/5  inches  on  the  inscribed  circle 
and  over  23  feet  long.  A  crack  developed  on  one  of  the  faces 
and  ran  down  a  short  way  on  the  second  face,  the  total  length 
visible  being  about  4  inches.  Attention  was  first  called  to  this 
by  rust  showing  through  the  paint  and  after  examining  the  shaft 
carefully  it  was  decided  to  run  the  steamer  to  see  if  the  crack 
extended.  Within  a  short  time  it  was  noticed  that  the  crack 
had  extended  3/4  inch  since  the  first  observation,  and  it  was 
therefore  decided  that  a  repair  of  some  sort  should  be  made  on 
it  at  once.  Preparations  were  made  to  weld  a  collar  of  Thermit 
steel  around  the  shaft  at  the  fracture  and  thus  to  restore  it  to  its 
original  state  of  usefulness.  A  pneumatic  chipping  hammer  was 
used  for  cutting  away  the  metal  to  the  bottom  of  the  flaw,  so 
that  the  superheated  Thermit  steel  could  be  led  to  the  deepest 
part.  After  this  had  been  accomplished,  the  paint  was  cleaned 
off  a  distance  of  5  inches  on  either  side  of  the  fracture  and  the 
weld  effected  by  the  wax  pattern  method,  as  previously  de- 
scribed; 416  pounds  of  Thermit,  35  pounds  of  mild  steel  punch- 
ings,  and  8  pounds  of  metallic  manganese  being  required.  After 

1  Ibid.,  Jan.  28,  1905. 

2  Iron  Age,  Nov.  16,  1905. 

3  Reactions,  published  by  Goldschmidt  Thermit  Co. 


148 


WELDING 


allowing  five  hours  for  the  metal  to  set,  the  mold  box  was  re- 
moved and  the  weld  found  to  be  so  satisfactory  that  the  steamer 
immediately  proceeded  on  her  trip  without  waiting  for  the  gate 
and  riser  to  be  cut  off;  in  fact,  the  repair  was  accomplished 
without  causing  the  steamer  to  miss  a  single  trip." 


FIG.  83. — Finished  weld  of  S.  S.  "Betsy  Anne"  before  removing  metal  left  in  gate 

and  riser. 

Repair  on  Steamship  "Corunna" 

"This  was  a  vessel  of  1296  tons  register,  240  feet  long,  35 
feet  beam  and  21  feet  depth.  In  getting  away  from  her  pier  in 
the  Lachine  Canal,  Montreal,  the  stern  of  the  vessel  was  caught 
by  the  current  and  swung  against  the  stone  walls  of  the  canal, 
the  shoe  or  skeg  being  broken  off  close  to  the  keel,  while  the 
rudder-post  was  broken  at  a  point  about  10  inches  from  the  top 
of  the  rudder.  Owing  to  the  serious  nature  of  the  injuries  it 
ordinarily  would  have  been  necessary  to  tow  the  vessel  to  Cleve- 
land (there  being  no  adequate  dry-dock  in  Montreal  to  make 
these  repairs  in  the  usual  way). 


THE    THERMIT   PROCESS 


149 


"It  was  soon  decided  that,  without  doubt,  several  thousand 
dollars  could  be  saved  by  repairing  the  frame  and  rudder-post 
with  Thermit. 

"  On  inspection  it  was  found  that  the  rudder-post  was  broken 
off  inside  of  the  tube,  while  the  stern  frame  had  been  bent  12 
inches  out  of  line,  the  shoe  being  completely  broken  about  13 
inches  from  the  central  line  of  the  post.  On  account  of  the 
break  in  the  rudder-post  being  by  an  old  scarf  weld,  fully  1 1 


FIG.  84. — Finished  weld  on  rudder  post  of  steamship  "Corunna." 

inches  in  length,  it  was  not  deemed  advisable  to  attempt  to  weld 
this  again,  so  about  14  inches  of  the  rudder-post  adhering  to  the 
rudder  was  cut  off  and  a  new  piece  of  shafting,  8  feet  long, 
welded  on  in  place  of  the  old  post,  as  shown  in  the  illustration. 
In  order  to  facilitate  the  operation,  the  rudder  was  removed 
from  the  ship  and  the  post  welded  on  shore,  this  being  done  to 
prevent  interference  with  the  operation  of  welding  the  stern  frame. 
"It  being  necessary  to  have  a  supply  of  compressed  air  in 
order  to  operate  the  gasolene  torch  and  pneumatic  tools,  an  old 
Westinghouse  steam-driven  air-brake  compressor  was  obtained 


WELDING 

and  mounted  on  board  ship,  the  steam  being  piped  from  a 
donkey  boiler.  A  receiving  tank  was  placed  on  the  edge  of  the 
boiler  and  piped  to  the  compressor.  With  the  apparatus  in 
place,  preparations  were  made  to  effect  the  welds  in  the  usual 
way,  the  rudder-post  weld  being  reinforced  by  a  collar  3  inches 
long  and  i  inch  thick,  while  the  stern-post  was  reinforced  with  a 
collar  8  inches  long,  i  inch  thick  at  the  top  and  sides,  and  3/4 


FIG.  85. — Thermit  weld  on  stem  post  of  steamship  "Sochem." 

inch  thick  at  the  bottom;  the  latter  being  done  in  order  that  the 
draught  of  the  vessel  might  not  be  made  any  greater  than  could  be 
helped.  One  hundred  and  fifty  pounds  of  thermit,  25  pounds  of 
steel  punchings,  and  3  pounds  of  metallic  manganese  were  used 
in  welding  the  rudder-post,  while  350  pounds  of  thermit,  70 
pounds  of  steel  rivets  (i  by  3/8  inch  in  size)  and  7  pounds  of 
metallic  manganese  were  required  for  welding  the  stern  frame. 
"While  the  total  time  required  for  the  operation  amounted  to 


THE    THERMIT   PROCESS 


five  working  days,  there  is  little  doubt  that  had  the  work  been 
done  in  a  properly  equipped  dry-dock,  it  could  have  been  ac- 
complished in  three  days  or  less." 


FIG.  86. — Weld  made  at  shops  of  the  central  railroad  of  New  Jersey  on  a  motor 

armature  shaft. 

Weld  of  Electric  Motor  Shaft 

"It  has  usually  been  deemed  necessary  to  leave  a  reinforce- 
ment or  collar  of  thermit  steel  around  the  various  welds  made 
by  the  thermit  process.  An  instance  has  occurred  recently, 


152  WELDING 

however,  where  this  reinforcement  was  machined  off  and  the 
weld  subjected  to  very  severe  strains,  but  without  causing  any 
weakness  to  show  up. 

"The  case  in  question  is  that  of  an  armature  shaft  3  inches  in 
diameter,  14  1/2  inches  long,  and  required  to  transmit  50  h.p. 
to  the  main  hoist  of  a  5o-ton  Shaw  electric  crane. 

"  The  weld  was  made  in  the  shops  of  the  Central  Railroad  of 
New  Jersey,  Elizabethport,  N.  J.,  and  the  armature  has  now  been 
in  service  since  October  8  and  is  giving  perfect  satisfaction  in  spite 
of  the  fact  that  all  the  surplus  metal  about  the  weld  was  machined 
off  and  the  shaft  turned  down  to  its  original  diameter. 

"The  weld  was  made  9  inches  from  the  hub,  and  is  shown  in 
the  accompanying  illustrations"  (Fig.  86). 

Chemistry  and  Thermics.— The  chemical  formula  for  the 
present  thermit  reaction  is 

8A1  +3Fe3O4  -  gFe  +4A12O3. 

Expressed  in  weights,  it  is 

217  parts  aluminum +732  parts  magnetite  =  540  parts  metallic 
iron  +409  parts  slag, 

or,  approximately,  3  parts  of  aluminum  and  10  parts  magnetite 
will  produce,  on  combustion,  7  parts  metallic  iron. 

Commerical  thermit  is  a  mixture  of  finely  granular  aluminum 
with  less  finely  granular  magnetic  iron  scale.  The  aluminum 
is  about  the  fineness  of  granulated  sugar;  the  scale  is  like  coarse 
sand.  The  ratio  by  weights  is  three  of  iron  scale  to  one  of  alum- 
inum. Dr.  Goldschmidt  began  his  experiments  with  similar 
mixtures  about  1895.  Thermit  was  not  heard  of  before  1902. 
He  speaks  with  feeling  of  the  mechanical  and  chemical  diffi- 
culties that  hindered  the  perfection  of  his  ideas.  So  there  is 
good  reason  to  suppose  that  the  thermit  mixture  is  about  the 
best  that  can  be  made,  both  in  its  physical  form  and  in  its  reac- 
tion. The  difficulties  that  confronted  Dr.  Goldschmidt  were: 

1.  The  violence  of  the  reaction. 

2.  How  to  get  a  good  homogeneous  steel  out  of  the  reaction. 
One  of  the  troubles  with  thermit  reactions  is  their  violence. 

The  burning  of  several  metals,  as  calcium,  is  so  brisk  that  the 
contents  of  the  crucible  boil  over  and  metal  and  slag  alike  are 


THE    THERMIT    PROCESS  1 53 

lost.  Probably  for  this  reason  the  magnetic  oxid  was  substituted 
for  the  hematite  oxid.  Early  literature  gave  the  reaction  as 

2A1  +Fe2O3  =  A12O3  +2Fe, 

but  Dr.  Goldschmidt1  gives  the  present  reaction  as  between 
aluminum  and  magnetite,  and  a  casual  examination  of  thermit 
by  means  of  a  magnet  shows  that  magnetite  is  now  used.  It  is 
likely  that  the  magnetic  oxid  gives  a  slower  burning  than  does 
the  sesquioxid.  The  magnetic  oxid  is  made  of  granulated  roll- 
ing-mill scale. 

The  aluminum  is  powdered  by  a  secret  process.  At  present 
there  are  two  known  ways  of  pulverizing  metallic  aluminum. 
The  first  is  to  raise  the  metal  to  an  approximate  600  deg.  Cent., 
at  which  heat  the  metal  becomes  brittle  and  granular,  and  can 
be  ground  between  rolls.  The  second  way  is  to  blow  air  through 
red-hot  aluminum  so  as  to  partly  oxidize  the  metal.  It  is  then 
cooled  to  about  600  deg.  Cent,  and  ground,  the  oxid  of  aluminum 
helping  to  separate  the  metal  into  fine  granules. 

As  will  be  guessed,  a  small  amount  of  thermit  will  burn  more 
slowly  than  a  large  amount.  The  heat  of  a  large  burning,  such 
as  for  repairing  a  propeller  shaft  or  large  engine  fly-wheel,  will 
be  so  intense  that  the  crucible  will  boil  and  throw  out  part  of 
its  contents.  To  prevent  this,  from  5  to  15  per  cent.,  by  weight 
of  thermit,  of  cold  steel  billets  and  turnings  are  added  to  the 
thermit  before  burning.  This  iron  takes  up  the  excess  heat. 
Of  course  this  added  steel  must  be  of  correct  chemical  composition. 

While  it  is  important  to  keep  down  the  boiling  reaction,  it  is 
even  more  necessary  to  get  a  resultant  steel  that  will  be  strong, 
elastic,  and  dense.  The  quality  of  the  thermit  steel  will  depend 
on  its  chemical  composition.  Good  steel  is  low  in  sulphur, 
phosphorus,  and  silicon,  and  not  too  high  in  carbon.  The  follow- 
ing "Average  Composition  of  Thermit  Steel"  is  given  by  the 
Company : 

Carbon 0.05  to  o.io 

Manganese 08  to     .10 

Silicon 09  to     .20 

Sulphur 03  to     .04 

Phosphorus ' 04  to     .05 

Aluminum 07  to     .18 

1  Electrochemical  and  Metallurgical  Industry,  Sept.,  1908. 


154  WELDING 

Of  course,  to  produce  a  steel  of  the  above  composition,  the 
aluminum  and  iron  scale  that  make  up  the  thermit  must  be  very 
pure.  It  would  be  a  problem  to  obtain  sesquioxid  of  iron  of 
sufficient  purity  and  at  the  same  time  as  cheap  as  rolling-mill 
scale.  Sesquioxid  or  hematite  ore  always  contains  one  or  the 
other  of  the  impurities  in  considerable  extent  and  is  of  variable 
composition;  while,  in  using  scale  from  Bessemer  or  open-hearth 
steel  the  impurities  would  be  already  known  and  would  be  much 
lower. 

In  regard  to  the  proportioning  of  the  mixture,  the  formula 
calls  for  3  parts  of  aluminum  to  10  of  iron  oxid;  the  thermit 
mixture  is  i  of  aluminum  to  3  of  the  oxid. 

In  nickel  thermit  the  reaction  is  2Al+3NiO  =  A12O3  +3Ni. 
By  weight,  it  is  54  parts  aluminum  and  224  parts  nickel 
oxid  give  176  parts  metallic  nickel.  Or,  approximately,  i  part 
aluminum  and  4  parts  nickel  oxid  give  3  parts  metallic  nickel. 
Nickel  thermit,  however,  contains  5  parts  of  nickel  oxid  by 
weight  to  5  of  aluminum. 

Besides  the  aluminum-iron  oxid  reaction,  a  number  of  others 
have  been  and  are  being  tried.  It  is  possible  that  the  future 
thermit  may  dispense  with  aluminum  and  substitute  another 
metal  for  reducer.  "  Weldite,"  an  English  product,  uses  silicon 
and  aluminum  with  Fe2O3.  Dr.  Goldschmidt  himself  has  tried 
other  combinations:  for  instance,  aluminum  and  calcium,  which, 
according  to  Dr.  Richards,1  give  a  greater  heat  due  to  the  forma- 
tion of  calcium-aluminum  slag.  He  gives  the  probable  formula 

5Fe203+3CaAl2  =  3(FeO.CaO.Al203)+7Fe; 

and  claims  that  70  per  cent,  of  the  iron  would  be  reduced  from 
its  oxide;  and  that  one  part  calcium-aluminum  alloy  will  produce 
one  and  four- tenths  of  liquid  iron  (metallic). 

Calcium1  alone  can  be  used  to  replace  aluminum,  but  the 
reaction  is  so  violent  that  sometimes  the  contents  fly  out  of  the 
crucible.  The  addition  of  30  to  40  per  cent,  fluor-spar  (CaF)  or 
10  to  20  per  cent,  quicklime  (CaO)  gives  a  saner  reaction. 

Heat  of  Reaction. — Richards2  has  calculated  the  heat  of  the 
thermit  reaction  as  2694  deg.  Cent.  The  temperature  commonly 

1  Engineering  and  Mining  Journal,  June  15,  1907. 

2  Electrochemical  and  Metallurgical  Industry,  J.  W.  Richards,  June,  1905. 


THE    THERMIT   PROCESS  155 

given  by  the  manufacturers  is  3000  deg.  Cent.  M.  Fery,  using  his 
new  radiation  pyrometer,  found  the  temperature  of  the  stream 
of  steel  as  it  flowed  from  the  crucible  to  be  2300  deg.  Cent — 
probably  about  right  when  one  makes  allowance  for  the  chilling 
effect  of  the  crucible.  Taking  the  melting  point  of  steel  as 
roughly  1350  deg.  Cent.,  the  thermit  steel  is  nearly  twice  as  hot. 

Testing. — The  strength  of  an  ordinary  weld  in  wrought  iron 
varies  from  10  to  almost  100  per  cent,  of  the  strength  of  an  equiv- 
alent cross-section  of  the  metal.  In  general,  however,  a  weld 
made  under  proper  conditions  runs  between  50  and  70  per  cent, 
for  high-carbon  iron  and  between  60  and  80  per  cent,  for  low- 
carbon  iron.  The  strength  of  a  thermit-weld  is  subject  to  quite 
as  great  variance,  for  the  reason  that  thermit  steel  is  a  definite 
compound  and  may  be  of  quite  different  composition  from  the 
parts  welded  by  it.  Also  it  is  well  to  bear  in  mind  that  the  initial 
strength  of  thermit  steel  itself  is  subject  to  variations  due  to  the 
amount  of  included  slag,  air  holes,  and  to  the  rapidity  of  cooling; 
also,  the  chemical  composition  can  be  varied  by  the  addition  of 
alloy  formers,  such  as  nickel,  chromium,  and  manganese;  and 
the  addition  of  titanium  and  manganese  in  small  quantities,  which 
are  purifiers. 

A  number  of  tests  of  different  character  have  been  made  by 
the  company  and  by  railroad  and  repair  shops,  some  of  the  results 
of  which  are  given  as  follows: 

Test  No.  i.1 

"At  the  St.  Louis  and  San  Francisco  Railroad  shops,  Spring- 
field, Mo.,  recently  the  following  test  of  a  thermit-weld  was  made: 

"  A  section  of  a  cast-steel  frame,  4  by  5  1/2  inches,  was  welded 
by  the  thermit  process.  In  making  the  weld  75  pounds  of  ther- 
mit, 12  pounds  of  punchings,  and  1 1/2  pounds  of  manganese  were 
used.  For  molds,  fire-brick  was  used,  cut  to  shape. 

"  After  the  weld  was  cold,  the  collar  on  the  bottom  and  one 
side  was  planed  off  1/4  of  an  inch  below  the  original  surface  of 
the  casting,  in  order  to  show  the  place  where  the  two  metals  had 
joined.  The  riser  also  was  cut  off,  leaving  the  collar,  however. 
The  weld  was  absolutely  solid,  not  a  single  blow  hole  appearing 
anywhere — not  even  the  riser. 

1  Reactions,  Vol.  I,  1908,  published  by  Goldschmidt  Thermit  Co. 


WELDING 


"The  welded  section  (now  3  3/4  x  5  1/4  inches),  with  collar 
i  inch  thick  on  top  and  on  one  side,  was  then  placed  in  wheel 
press  on  supports  14  3/4  inches  apart  and  a  piece  of  hardened 
steel,  i  inch  square,  placed  as  shown  in  figure  87. 

"A  pressure  of  170  tons  was  applied  before  breaking.  The 
fracture  started  at  the  bottom  outside  welded  section,  extending 
into  the  center  of  the  weld  at  the  top.  The  fracture  showed  that 
perfect  amalgamation  of  the  metals  had  taken  place. 

"In  comparing  the  strength  of  this  weld  with  original  stock, 
assuming  a  maximum  stress  in  the  outer  fiber  for  cast  steel  of 


Plunger 

^-l"x  I  Steel  Block 


! 

[Weld  J 


FIG.  87. — Arrangement  of  test  piece  for  test  No.  i. 

60,000  pounds  to  the  square  inch,  a  section  3  3/4  x  5  1/4  inches 
tested  in  the  same  way  would  break  at  100  tons." 

In  this  test  No.  i  it  is  presumed  that  the  12  pounds  of 
punchings  were  mild  steel.  The  manganese  was  used  to  freshen 
the  iron,  and  most  of  it  probably  slagged  as  manganese  oxid  and 
came  to  the  surface. 

Test  No.  2.  1 

"Two  test  bars  taken  from  the  upper  part  of  a  previously, 
but  unsuccessfully,  poured  casting  gave,  on  an  average,  66,000 
pounds  per  square  inch  tensile  strength  and  9 .  5  per  cent,  elonga- 
tion on  a  measured  length  of  2  inches.  This  casting  showed  in 
all  the  sections  a  clean,  non-porous,  dense  grain.  It  appears 
possible,  therefore,  to  produce  steel  castings  of  thermit  and,  in  a 

1  Iron  Age,  April  26,  1906. 


THE    THERMIT    PROCESS  157 

case  of  necessity,  the  higher  price  would  not  be  of  importance." 

Test  No.  3. 

The  thermit  process  has  been  used  by  the  Fore  Shipbuilding 
Co./  of  Quincy,  Mass.,  who  have  made  a  number  of  tests  of  the 
physical  properties  of  thermit  metal.  Bars  of  rolled  steel,  of 
section  2x4  1/2  inches  were  drilled,  broken,  and  welded  with 
thermit.  Standard  test  bar  were  cut  from  the  centre  of  the 
welded  bar,  and  were  submitted  to  the  ordinary  tests.  As  the 
test  pieces  were  of  uniform  size,  both  in  the  stock  and  the  welded 
section,  the  result  is  worth  recording: 


Elastic  limit 

Tensile  strength 

Weld  

32,000 

59,000 

Stock  

38,000 

60,500 

Weld  

33,700 

61,800 

Stock  .          

36,8^0 

63,400 

It  is  to  be  noticed  that  the  tensile  strength  is  12.7  per  cent, 
less  in  the  weld  than  in  the  stock,  and  the  tensile  strength  2 . 5 
per  cent,  less — a  fair  showing. 

Test  No.  4.— By  the  Illinois  Steel  Co.,  Chicago.2 


Tensile  strength 59>320  Ibs. 

Elongation    25  •  33  Per  cent- 
Contraction  of  area ...    59.9     per  cent. 


Test  No.  5.— By  the  Pennsylvania  Railroad,  Altoona,  Pa.3 


Tensile  strength 91,600  Ibs. 

Elongation  in  8" 21.5     per  cent. 

Silky  fracture. 


1  Journal  United  States  Artillery,  Gustav  Reiniger,  July-August,  1907. 

2  Transactions  of  the  Society  for  Testing  Materials,  E.  Stutz,  1905. 

3  Transactions  of  the  Society  for  Testing  Materials,  E.  Stutz,  1905. 


c 

.   o.o< 

Mn    ... 
Si 

10 

...                204 

S 

.  04. 

P 

•  O< 

Al    . 

.18 

c 

O.  IO2 

Mn 

2  .  "?  3O 

Si 

.     I  .  227 

S                        .    . 

.0^4 

P   . 

.07 

158  WELDING 

Test  No.  6. — It  has  been  suggested  that  the  thermit-weld 
may  be  strong  in  itself,  but  that  it  weakens  the  adjacent  iron.  To 
find  if  this  is  so,  a  section  of  welded  rail  was  subjected  to  equal 
blows  by  a  steam  hammer,  both  on  the  unaffected  rail  and  on 
the  metal  nearest  the  weld.  The  die  used  was  a  blunt  tool,  1/4 
inch  in  diameter.  Measurement  with  a  micrometer  showed  a 
depression  of  o.  1432  inch  in  the  rail  nearest  the  weld  and  o.  1596 
inch  3  feet  from  the  weld. 

Tests,  under  varying  conditions  without  number,  might  be 
multiplied.  But  for  the  practical  man,  those  already  given  show 
that  the  ultimate  strength  of  the  thermit  steel  in  practice  can  be 
estimated  as  over  30  tons  to  the  inch  section.  By  practice,  I 
mean  the  thermit  steel  produced  for  repair  work,  according  to 
directions:  thermit,  about  51  per  cent,  mild  steel  punching,  and 
about  22  per  cent,  manganese  for  purifier. 

Annealing  for  3  hours  brings  the  elongation  well  over  10  per 
cent. 

Addition  of  about  32  percent,  nickel  raises  the  ultimate  strength 
about  5  tons  without  decreasing  the  elastic  limit.  Further  addi- 
tion of  about  22  per  cent,  of  chromium  with  the  nickel  brought  the 
elastic  limit  to  about  47  tons — as  high  as  can  be  wished.  Addi- 
tion of  i  per  cent,  titanium  raises  the  tensile  strength.  Tests  have 
also  been  made  of  thermit  steel  that  has  been  toned  up  with 
molybdenum,  ferro-silicon,  etc. 


THE  LAFITTE  WELDING  PLATE. 

The  Lafitte  process  was  first  heard  of  in  1905.*  It  may  be 
described  as  the  handy  application  of  a  patent  fluxing  sheet  be- 
tween parts  to  be  welded,  and  can  only  be  used  for  joining  iron 
and  steel.  The  flux  is  sold  as  a  plate,  size  4  by  8  inches  and 
about  i/i 6  inch  thick.  This  plate  is  composed  of  a  preparation 
of  calcined  borax  and  iron  filings,  molded  over  a  sheet  of  wire 
gauze.  The  gauze  is  about  15  meshes  to  the  inch  length. 

1  Calculated  from  weight  of  thermit  powder. 

2  Calculated  from  weight  of  test  bar. 

3  Iron  Age,  May  n,  1905. 


THE    LAFITTE    WELDING    PLATE 


The  iron  of  the  wire  is  low-carbon  (0.08  per  cent,  by  color 
determination1). 

The  pieces  to  be  welded  are  brought  to  the  welding  heat  and 
forced  together  with  a  Lafitte  plate  between  the  contacts.  As 
with  all  smith-welding,  one  of  the  contact  surfaces  should  be 
decidedly  convex,  so  that  the  point  of  it  is  first  brought  to  bear 
on  about  the  middle  of  the  other  contact  surface.  As  the  two  sur- 
faces are  forced  together,  with  the  plate  between,  the  borax  melts 
and  flows  out,  fluxing  both  surfaces  as  it  flows.  The  iron  gauze, 
which  is  inside  the  plate,  is  also  partly  melted  and  welds  itself  in 
place  on  both  surfaces.  It  is  likely  that  the  strength  of  the  Lafitte 
weld  is  as  much  due  to  the  binding  action  of  this  low-carbon  iron 
wire  as  it  is  to  the  complete  fluxing  of  the  borax.  If  properly 
done,  the  weld  should  be  flawless.  It  is  not  necessary  to  use  more 
of  the  plate  than  will  cover  both  surfaces.  The  plate  can  be  cut 
with  ordinary  shears. 

From  tests  made  it  is  claimed  that  the  Lafitte  weld  is  as  strong 
as  the  metal,  in  case  soft  steel  is  welded;  but  that  in  high-car- 
bon steel  there  is  a  slight  lowering  of  the  elongation  and  tensile 
strength  (due  no  doubt  to  the  reheating  of  a  specially  treated 
product). 

In  all  but  one  of  these  tests  the  tensile  strength  is  greater  for 
the  Lafitte  weld  than  for  the  body  of  the  stock,  which  may  indicate 
that  an  upset  of  metal  was  crowded  into  the  weld  by  the  pressure 
of  welding;  while  with  cast  steel  the  quality  of  the  metal  might 
be  improved  by  the  pressure. 

Hard  Steel  Test 
Mn,  1.35;  C,  0.45;  S,  0.045;  P,  0.083;  Si,  0.08 


Tensile  strength,  kg.  . 

Before  welding 

Lafitte  weld 

Common  weld 

70 

63.6 
68. 

55-9 

Elongation,  per  cent.  . 

15.2 

10.0 

ii.  6 

2-5 

Specially  analyzed. 


l6o  WELDING 

Test  by  the  French  Government1 — (Toulon  Arsenal) 


Tensile  strength,  Ibs. 

Elongation,  per  cent. 

Before 

Special 
compound 

Lafitte 

Before 

Special 
compound 

Lafitte 

Iron  on  iron  

48,700 

44,720 

48,038 

1  6.  33 

9.66 

14.  -3  •? 

Iron  on  soft  steel  

48,700 

43>964 

45,631 

16.33 

4-— 

4-  — 

Steel  on  soft  steel  .... 

75.935 

72,197 

80,500 

2.  

I.  

2.— 

Iron  on  cast  steel  .... 

75,935 

43,7*9         78,692 

2.  

3-25 

9-°5 

Cast  steel  on  cast  steel. 

95,030 

92,712       102,711 

5.62 

3-  — 

5-  — 

The  Lafitte  method  may  suggest  itself  for  stock  welds,  such 
as  the  joining  of  axle  parts  and  in  chain  making;  in  other  words , 
in  instances  of  multiple  welding,  where  the  pressure  machinery 
is  handy.  It  is  most  used  in  France  and  Germany. 

FERROFIX  BRAZING  PROCESS 

An  ingenious  and  very  good  modern  method  of  brazing 
broken  iron  parts  (especially  cast  iron)  goes  by  the  name  of  the 
Ferrofix  Brazing  Process.  It  was  devised  by  Frederick  Pich,  a 
German.  By  this  process  two  fractured  pieces  of  iron  are  ce- 
mented together  with  a  thin  film  of  brass  which  is  so  applied  that 
it  alloys  with  the  iron  surfaces,  as  deep  as  1/16  inch.  This 
was  proven  by  cutting  open  a  brazed  joint  and  planing  it 
down  to  ascertain  its  structure.  To  get  this  alloy  in  the  joint, 
which  is  the  secret  of  its  strength,  the  solder  must  not  melt  below 
650  deg.  Cent. ;  hence  hard  brass  is  used. 

Apparatus  for  Ferrofix  repairing  consists  of: 

1.  A  kerosene  pressure  tank  and  two  or  more  Donnelly  torches, 
which  is  an  improved  non-carburizing  kerosene  burner. 

2.  Fire-bricks  and  asbestos  paper  for  a  small  furnace. 

3.  Ferrofix  fluxing  powder. 

4.  Patent  brazing  liquid. 

The  torch  for  heating  may  be  air-coal  gas,  air-oil,  oxy-acety- 
lene,  etc. 

The  flux  is  a  mixture  of  equal  parts  of  sodium  carbonate  and 
boric  acid,  with  a  little  common. salt  to  increase  fluidity. 

llron  Age,  August  24,  1905. 


FERROFIX    BRAZING    PROCESS  l6l 

United  States  patent  paper,  No.  688030,  states  that  borax, 
the  chief  flux  for  all  soldering  and  brazing,  is  troublesome  be- 
cause it  swells  up  and  falls  off  of  the  piece  as  soon  as  heat  is 
applied.  This,  because  it  is  then  parting  with  water  of  crystal- 
lization. The  patent  flux,  on  the  other  hand,  acts  as  follows:  the 
carbonate  is  a  ready  absorbent  of  grease,  of  which  it  frees  the 
the  iron  surface.  With  the  application  of  heat,  the'carbonate  also 
reacts  on  the  boric  acid,  forming  anhydrous  borax  and  carbon 
dioxid.  The  borax  is  thus  in  close  contact  with  the  fresh  metal 
surface,  which  it  frees  of  rust  and  protects  from  the  air. 

The  soldering  compound  is  described  in  patent  No.  647632  as 
follows : 

"To  form  my  improved  soldering  compound,  I  boil  together 
finely  pulverized  borax  and  finely  pulverized  suboxid  of  copper, 
so  that  the  same  are  intimately  mixed  and  so  that  each  particle 
of  the  suboxid  of  copper  is  surrounded,  covered,  and  protected 
from  the  atmosphere  by  a  thin  film  of  the  borax.  Any  desired 
proportions  of  the  two  may  be  used;  but  usually  I  take  one-half 
of  each,  mixed  with  sufficient  water  to  dissolve  the  same  thoroughly 
by  the  boiling,  and  to  cool  down  into  a  sort  of  paste. 

"  To  use  this  soldering  compound,  the  cast-iron  surfaces  to  be 
soldered  are  cleaned  by  means  of  an  acid  in  the  usual  way,  fixed 
together,  and  the  joints  covered  or  surrounded  with  the  compound. 
The  joint  is  then  heated,  and  therefore  the  borax  melts  and  pro- 
tects the  cleaned  surface  of  the  iron  against  oxidization,  removes 
any  oxid  thereon,  and  also  protects  the  suboxid  of  copper  against 
the  action  of  the  oxygen  of  the  atmosphere.  Consequently 
the  suboxid  of  copper,  likewise  heated  to  a  red  heat,  transfers 
its  oxygen  to  the  red-hot  cast-iron  surface,  which  oxygen  com- 
bines with  the  graphite  contained  in  the  cast-iron  surfaces  to 
form  carbon  monoxid  or  dioxid,  thus  decarbonizing  said  surfaces, 
while  the  metallic  copper  becomes  dissociated  in  a  very  finely 
divided  condition.  At  the  same  time  the  hard  solder  is  added, 
and  as  this  solder,  which  is  brought  upon  the  surfaces  to  be  sol- 
dered in  the  well-known  manner,  is  likewise  melted  by  the  heat, 
it  alloys  itself  with  the  incandescent  particles  of  copper,  and  this 
new  alloy  immediately  combines  with  the  red-hot  decarbonized 
soldering  surfaces  of  the  cast  iron." 


1 62  WELDING 

The  company  also  issue  instructions,  which  are  in  brief: 

i.  "  Clean  fractured  surfaces  thoroughly  with  wire  brush.  If 
rusty  or  oily,  burn  off  with  torch. 

"  2.  Mix  Ferrofix  powder  with  the  brazing  liquid  to  the  con- 
sistency of  paint  and  apply  on  the  fractured  surfaces  with  brush. 

"  3.  Set  casting  to  be  brazed  on  fire-brick,  in  perfect  alignment, 
using  fire-clay  to  hold  it  in  place  (if  it  will  not  stay  of  its  own  weight) . 
Be  sure  that  the  broken  parts  fit  close.  Build  a  furnace  of  fire- 
brick around  the  fractured  part,  allowing  sufficient  metal  to  be 
exposed,  however,  to  absorb  the  heat.  Leave  top  of  furnace 
open,  covering  only  with  a  sheet  of  asbestos — 3/16  inch  thick  is 
sufficient  ordinarily.  The  front  of  furnace  should  be  left  open  to 
admit  the  torch  blast. 

"4.  Place  the  torches  so  that  the  flame  will  come  directly  on 
fracture;  bring  casting  up  to  a  light  cherry-red,  almost  straw. 
See  that  both  sides  of  the  fracture  keep  at  the  same  color. 

"  5.  Apply  flux  with  a  steel  spoon  (made  from  3/8-inch  Besse- 
mer steel  rod  flattened  out  at  one  end)  holding  it  at  the  fracture 
with  the  spoon,  so  that  from  the  heat  of  the  casting  (not  the 
torch  alone)  it  will  melt  and  disappear  through  the  crack.  As 
soon  as  it  comes  through  freely  and  you  can  see  the  liquid  flux 
underneath,  apply  spelter  with  a  very  little  flux;  feed  this  until 
it  flows  through  thoroughly.  With  the  spoon  the  melted  brass 
can  be  taken  from  underneath  and  fed  over  until  the  crack  com- 
mences to  fill,  then  cut  off  immediately  your  air  and  gas,  and  keep 
feeding  a  little  more  new  brass  until  it  will  not  melt  further  by 
heat  of  casting.  Allow  to  cool  down  by  its  own  cooling. 

"  6.  Clean  casting  with  file,  chisel,  or  emery  wheel. 

"The  question  of  expansion  and  contraction  is  governed  by 
the  construction  of  the  casting  and  the  character  of  the  metal. 
Care  should  be  taken  to  see  that  heat  is  properly  applied  and 
distributed  to  overcome  this  feature.  Experience  on  intricate 
castings  is  the  best  teacher." 

This  is  another  comparatively  new  process  that  is  beginning 
to  be  known  by  the  foundries,  car  shops,  blast  furnaces,  and 
machine  shops.  The  first  patent  dates  1900.  Its  success  is 
based  on  its  cheapness,  handiness,  and  strength.  The  initial 
expenditure  is  very  low,  the  burner  costing  most.  The  outfit 


FERROFIX    BRAZING    PROCESS 


would  prove  a  great  saving  to  any  plant  which  has  breaks  in  its 
iron  machine  parts.  For  a  fractured  piece  could  be  mended  in 
an  hour,  whereas  it  is  ordinarily  necessary  to  rivet  the  old  piece 
together  with  side  braces  or  to  order  a  new  piece  under  danger  of 
delay  and  hold  up. 

As  for  strength,  the  company  guarantees  that  the  joint  is 
stronger  than  cast  iron;  brazed  pieces  never  break  in  the  joint. 
Moreover,  the  pieces  to  be  mended  are  set  as  closely  as  possible, 
as  the  spelter  will  penetrate  the  tightest  fracture. 

There  are  "several  tests  covering  the  penetration  of  brass  on 
cast  iron  treated  with  Ferrofix  and  also  untreated.  This  was 
done  by  the  taking  three  test  bars  which  had  the  upper  surface 
smooth,  one  was  left  uncoated,  one  had  one  coat  of  Ferrofix 
applied,  and  the  third  had  two  coats  of  Ferrofix.  They  were 
then  placed  in  the  furnace  and  heated  to  the  same  temperature, 
and  the  surface  coated  with  brass  as  in  brazing.  When  cold 
the  coated  surface  was  planed  1/32  inch  below  the  original  surface. 
We  found  on  the  untreated  piece  no  evidence  of  brass,  while 
on  the  treated  pieces  brass  was  distinctly  discernible  in  the  pores 
of  the  iron.  Another  1/32  inch  was  then  taken  from  the  two 
treated  pieces,  and  we  found  on  the  bar  that  had  a  single  coating 
of  Ferrofix  minute  traces  of  brass,  while  on  the  double-coated 
piece  the  brass  was  very  distinct.  It  must,  therefore,  be  apparent 
that  the  joint  we  obtain  is  not  simply  a  surface  adhesion,  but  an 
actual  anchoring  of  the  filling  material  to  the  adjacent  faces  of 
the  fracture."1 

Tests  Made  by  Riehle  Bros. 

Specimens  6"  x  6"  x  24"  long.     Cast  iron.     Supports  20"  apart.     Load  applied 
at  center  of  specimen. 


Marked 

Breaking  strength  in  Ibs. 

After  brazed 

i 

155,280 

131,000 

2 

178,700 

180,860 

3 

194,440 

187,750 

4 

168,700 

178,310 

5 

163,220 

162,450 

Special  information. 


164 


WELDING 
Tests  Made  by  Riehle  Bros. 


Marked 

Area  in  sq. 
inches 

Ultimate  strain 
persq.  in.inlbs. 

Remarks 

No.  i.  Brazed 
No.  2. 
No.  3.  Solid 

•450 
•439 
•439 

19,220 
20,570 
22,730 

Broke  outside  weld 
Broke  outside  weld 
Broke 

Two  other  tests  by  the  same  company  showed  increases  of 
i  and  6  per  cent,  for  mended  bars. 

Of  three  tests  by  Lewis  Foundry  and  Machine  Co.,  the  first 
showed  an  increase  in  strength  of  i,  and  the  other  two  a  decrease 
of  14  and  29  per  cent. 

Two  bars  tests  by  Cramp's  broke  outside  the  joint. 


FIG.   88. — Broken  arm  that  was  made  stronger  than  originally  by  the  ferrofix 

brazing  process. 

The  process  is  now  used  for  all-sized  repairs,  small  or  very 
large. 

"By  accident  a  spoke  was  broken  from  a  fly-wheel,  19  feet  in 
diameter,  48  inches  width  of  rim,  weighing  21  tons.  A  new 
wheel  would  have  cost  $2700  and  would  have  involved  two  or 
three  months'  delay.  The  Pich  process  was  applied;  the  broken 


BRAZING   AND    SOLDERING  165 

spoke  was  brazed  into  place,  and  $250  charged  and  paid  for  the 
job.     The  actual  cost  of  doing  this  work  was  less  than  $50.* 

Figure  88  shows  a  break  of  an  important  appliance  that  can 
be  mended  by  this  process. 

BRAZING  AND  SOLDERING 

Brazing  and  soldering  are  processes  which  are  much  like 
welding  and  which  often  shade  over. into  welding.  The  brazing 
of  brass  is  welding,  except  that  the  metal  is  not  pounded  together, 
but  melted.  The  definitions  for  soldering  and  welding  are  given 
in  the  first  chapter.  Brazed  and  soldered  joints  resemble  welded 
joints  in  as  far  as  the  solder  and  the  metal  of  the  piece  or  utensil 
amalgamate  at  the  joint.  But  such  joints  are  different  from 
welded  joints  because  the  solder  or  spelter  is  of  different  com- 
position from  the  metals  it  joins  and  serves  the  purpose  of  a 
go-between. 

Brazing. — Iron,  brass,  copper,  gold,  and  silver  are  the  metals 
joined  by  brazing.  The  process  is  briefly:  fluxing  the  metals 
at  the  joint,  adding  the  brazing  mixture  called  "spelter,"  heating 
until  the  spelter  melts  and  works  into  the  joint,  finishing  the 
brazed  joint  with  the  proper  tools. 

The  flux  used  is  either  borax  or  boracic  acid.  The  latter 
is  used  because  it  is  cheaper;  but  for  other  than  rough,  commercial 
work  borax  is  the  btter.  Borax  should  be  burnt  or  calcined 
before  using  to  drive  off  the  water  of  crystallization.  If  this  is  not 
done,  the  borax  will  swell  up  under  the  flame,  will  blister,  jump, 
and  much  of  it  be  lost.  Whereas  calcined  borax  simply  melts  on 
the  metal,  runs  over  the  surface  in  a  thin  glass,  and  cleans  the 
surface  of  oxid  and  grease. 

Before  applying  the  flux,  it  is  well  to  clean  the  metal  with  a 
file  and  remove  all  grease  with  a  rag  or  alkali  water. 

Besides  borax  there  are  a  number  of  other  chemicals  which 
can  be  used,  such  as  zinc  chlorid,  sal  ammoniac,  common  salt, 
and  the  corrosive  acids.  None  of  these  are  as  good  as  borax. 
The  first  two  are  properly  soldering  fluxes,  the  third  melts  too 
readily,  and  the  acids  are  liable  to  remain  in  the  brazed  joint 
and  to  decompose  it  slowly. 

Proclamation  of  the  Boston  Society  of  Civil  Engineers,  May  20,  1903. 


166 


WELDING 


A  number  of  patent  powders  and  liquid  fluxes  are  now  on  the 
market.  They  are  mixtures  of  the  common  fluxes  in  such  form 
that  they  can  be  easily  applied  to  the  work. 

Spelter  for  brazing  is  used  to  cover  a  range  of  hard  and  soft 
alloys,  though  spelter  is  supposed  to  be  a  half-and-half  alloy  of 
copper  and  zinc.  Hobart1  gives  the  following  table  of  brazing 
alloys : 


Brazing  alloys 

Tin 

Copper 

Zinc 

Antimony 

Hardest  

0 

3 

i 

0 

Hard  (spelter)  

0 

i 

i 

0 

Soft 

i 

3 

o 

Softest  

2 

0 

0 

, 

English  books  mention  spelter  as  composed  of  i  part  of 
fine  brass,  i  part  zinc — in  other  words,  2  parts  zinc,  i  part  cop- 
per. The  hardest  spelter  will  give  the  strongest  joint,  provided 
the  spelter  amalgamates  perfectly  at  the  joint.  It  will  also 
require  the  hottest  flame  to  melt  and  will  be  more  difficult  to 
handle.  Softer  spelters  give  softer  joints,  work  in  easier,  and  are 
cheaper  to  handle.  Brass  and  iron  joints  that  do  not  have  to 
stand  strain  nor  long  time  test  are  brazed  with  softer  spelters. 
Spelter  is  powdered  or  filed  into  shavings,  and  mixed  with  the 
flux;  or  it  is  cut  into  thin  strips  or  small  chunks. 

The  torch,  for  brazing  or  soldering,  is  used  when  the  work  is 
not  on  a  large  piece  or  when  a  forge  is  not  handy.  A  gasoline 
or  kerosene  torch  can  be  used  for  small  work.  A  blacksmith's 
forge  is  better,  because  the  piece  can  be  heated  slowly  and  evenly, 
and  cooled  the  same  way.  The  same  restrictions  apply  for  all 
fuel  used  as  apply  for  welding  (see  page  4).  The  fuel  should 
be  free  from  sulphur  and  soot  and  the  flame  should  be  non- 
oxidizing.  In  the  case  of  coal  and  coke,  do  not  let  the  fuel  touch 
the  parts  to  be  brazed. 

As  in  welding,  a  gas  flame  is  the  best.  The  operator  can  build 
up  a  furnace  of  fire-brick,  with  one  or  more  nozzles  of  gas  pipe 

1  "Brazing  and  Soldering,"  James  F.  Hobart,  1908. 


BRAZING    AND    SOLDERING 


I67 


intruding.  He  can  then  regulate  the  size  and  direction  of  the 
flame,  and  heat  and  cool  the  work  slowly  and  evenly. 

Brazing  work  requires  high  temperatures:  for  iron  it  is  done 
at  a  bright  red,  almost  white,  heat.  This  explains  why  the  flame 
should  be  reducing  and  free  from  sulphur. 

The  gas  flame  varies  from  a  blowpipe  flame  to  that  given  by 
a  two-way  injector  tube  made  of  gas  piping  (see  Fig.  89).  The 
flame  is  a  bunsen  flame,  with  a  blue  cone. 

To  braze  requires  considerable  variation  in  practice,  accord- 
ing to  the  work  at  hand.  Suppose  the  worker  is  about  to  braze 


FIG.  89. — Air-gas  torch  for  brazing. 

together  two  cast-iron  pieces  of  a  fractured  bar.  He  first  cleans 
the  ends  of  the  bar  at  the  fracture  by  filing  and  scraping  away 
all  grease  and  paint  and  then  cleans  the  fracture  with  a  wire 
brush.  He  then  brushes  the  borax  on  the  fresh  surfaces  or,  in 
case  a  liquid  preparation  is  used,  he  applies  it  with  a  brush. 
He  then  places  the  pieces  together  as  he  intends  to  braze  them, 
resting  them  on  fire-brick,  and  builds  up  a  little  oven  of  brick 
around  and  over  the  pieces,  leaving  one  wall  of  the  oven  open 
for  the  flame  (see  Fig.  90).  When  brazing  pieces  or  mending 


i68 


WELDING 


fractures,  always  press  the  surfaces  as  closely  together  as  possible. 
No  joint  is  too  tight  for  the  spelter  to  enter,  while  the  tightest 
joint  will  be  the  strongest. 

The  burners  are  then  brought  up  in  front  of  the  open  oven 
and  pointed  at  the  work.  These  burners,  for  job  work,  are  com- 
monly made  of  two-way  gas  pipe  with  rubber  hose  for  leading 
tubes.  One  tube  carries  the  gas,  the  other  the  air  blast.  The 
air-blast  tube  is  straight  and  draws  in  the  gas  by  injection.  The 
air  blast  is  made  by  a  motor-driven  fan.  For  convenience  these 
gas-pipe  torches  are  swiveled  on  tripods.  The  air  blast  is 
started,  the  gas  turned  on,  and  the  operator  regulates  the  flame 


FIG.  90. — Makeshift  brick  furnace  for  brazing;  showing  broken  casting  in  position. 

to  an  even  blue  cone  by  turning  the  cocks.  The  flame  is  di- 
rected at  the  work  and  kept  there  until  the  brazing  is  done.  At  a 
bright  red  heat,  the  operator  sprinkles  more  brazing  powder  or 
borax  on  the  edges  of  the  fracture,  and  works  it  back  and  forth 
with  an  iron  spatula.  This  cleans  the  iron  surfaces  at  the 
fracture,  so  that  the  spelter  will  wet  the  iron  and  run  down  into 
the  fracture;  next  he  shovels  some  spelter  over  the  fracture  and 
works  it  back  and  forth  as  it  melts  down.  If  the  fluxing  has  been 
right,  the  spelter  will  slip  down  into  the  crack  and  fill  up  the  entire 
fissure,  wetting  the  iron  surfaces,  and  the  excess  will  run  out  of 
the  lower  crack  of  the  fracture. 

The  operator  now  turns  off  the  flame  and  allows  the  work  to 
cool.     Cast  iron  will  cool  quickly;  but  if  the  piece  to  be  mended 


BRAZING    AND    SOLDERING  169 

is  at  all  intricate  or  has  long  arms,  care  must  be  taken  to  allow 
for  equal  cooling  and  shrinkage. 

Care  must  be  taken  in  heating  the  work  to  be  brazed  that  the 
heating  is  done  evenly  and  that  no  part  is  overheated.  In  the 
case  of  brass,  overheating  spoils  the  metal  as  it  burns  out  the 
zinc  to  some  extent.  A  safe  method  in  brazing  brass  is  to  paint 
the  piece  over  with  a  graphite  preparation,  except  where  the 
brazing  is  to  be  done.  The  graphite  is  indifferent  to  flame  and 
flux  and  will  prevent  the  zinc  from  volatilizing.  One  of  the 
objections  to  soft  spelter  is  the  amount  of  zinc  it  contains. 

In  the  making  of  a  number  of  utensils  brazing  plays  an  impor- 
tant part.  For  this  reason  it  is  important  to  do  the  work  quickly. 
Much  repeat  or  stock  brazing  is  now  done  by  immersion,  the  same 
as  iron  is  tinned.  The  pieces  to  be  brazed  are  painted  with 
graphite  wherever  necessary,  are  heated,  and  then  plunged  into  a 
bath  of  melted  spelter,  on  the  top  of  which  floats  the  melted  flux. 
The  flux  cleans  all  of  the  metal  unprotected  by  the  paint,  and 
then  as  the  pieces  are  lowered  further  into  the  bath,  the  melted 
spelter  readily  wets  the  fluxed  surfaces  and  brazes  the  pieces. 

In  brazing  gold  and  silver,  the  alloy  used  is  commonly  a 
mixture  of  spelter  with  gold  and  silver;  sometimes  antimony, 
arsenic,  etc.,  being  added  to  reduce  the  melting  point  and  to  make 
the  alloy  fluid.  This  means  that  the  process  is  really  a  soldering 
one.  Brazing  of  gold  and  silver  is  a  jeweler's  art.  It  is  done  with 
small  pieces  and  needs  only  a  foot  blast  or  a  mouth  blowpipe  for 
the  flame. 

A  brazed  joint  is  commonly  considered  to  be  stronger  than 
the  adjacent  metal.  A  brazed  cast-iron  piece  will  never  frac- 
ture at  the  braze.  Tests  of  well-brazed  joints  show  them  to 
to  be  from  10  to  25  per  cent,  stronger  than  the  iron.  A  brazed 
joint  is  inferior  in  a  number  of  ways  to  a  welded  joint.  In  the 
first  place,  the  electrical  conductivity  is  not  equal  to  the  piece 
brazed.  Then  there  is  the  danger  that  free  acid,  pieces  of  flux 
or  rust  have  been  left  in  the  joint  and  will  lessen  the  strength  at 
once  or  by  slow  action.  Then,  under  water,  a  brazed  joint  may 
become  an  electric  couple,  and  the  metal  may  slowly  disinte- 
grate. Lastly,  it  is  found  that  brazed  joints  will  not  stand  concus- 
sion tests  as  well  as  welded  joints.  This  is  attributed  to  the 


1 70  WELDING 

presence  of  zinc,  which  is  said  to  weaken  the  joint  by  its  presence 
in  the  alloy. 

Aside  from  these  objections,  a  brazed  joint  is  apt  to  be  stronger 
than  a  weld,  is  generally  cheaper,  easier  to  make,  takes  less  skill, 
apparatus,  and  time,  and  is  often  quite  good  enough  for  the 
purpose. 

Soldering. — A  solder  is  a  metallic  glue.  There  are  almost 
an  infinite  number  of  solders,  the  most  common  being  lead-tin 
solder  for  soldering  the  common  commercial  metals.  The  lead- 
tin  proportion  is  varied  to  obtain  solders  with  different  melting 
points,  strength,  fluidity,  and  elasticity.  Then  other  metals 
are  added  to  the  original  lead-tin  alloy,  so  that  the  properties  of 
the  solder  are  given  a  different  range.  The  solder  may  be  used 
for  special  metals  and  special  purposes.  Either  the  lead  or  tin 
or  both  may  be  dropped. 

All  solders  have  lower  melting  points  than  the  metals  they  are 
intended  to  join;  all  solders  must  amalgamate  with,  or  "wet," 
the  metals  they  join.  Most  solders  are  weaker  in  tensile  strength 
than  the  joined  metals.  For  this  reason  soldered  joints  are  not 
often  intended  to  be  specially  strong.  When  metals  are  soldered 
in  preference  to  being  brazed  or  welded,  it  is  because  time  and 
money  can  be  saved  and  a  satisfactory  joint  gotten. 

Ordinary  solder  is  half-tin  half-lead,  by  weight.  Hard  solder 
is  two  parts  lead  to  one  part  tin.  Hard  solder  is  more  brittle, 
stronger,  and  has  a  higher  melting  point.  On  account  of 
the  present  high  price  of  tin,  it  is  also  cheaper.  To  ordinary 
solder,  antimony  is  added  to  still  further  harden  and  stiffen  the 
solder.  Arsenic  is  sometimes  added  to  make  the  melted  solder 
flow  freely.  Bismuth  and  cadmium  are  sometimes  added  to 
bring  the  melting  point  down.  For  example,  Wood's  metal  con- 
tains two  tin,  two  lead,  two  cadmium,  and  eight  bismuth,  and 
melts  at  70  deg.  Cent.  Bismuth  is  apt  to  make  a  solder  brittle; 
while  cadmium,  like  tin,  helps  to  make  the  solder  elastic  or  soft. 
Copper  in  small  proportion  will  stiffen  and  strengthen  solder, 
but  it  will  raise  the  melting  point  sharply.  Iron  is  seldom  used 
in  solders. 

The  data  on  the  proportions  of  these  metals  in  the  solders  is 
very  inexact,  and  the  exact  properties  of  a  given  alloy  are  seldom 


BRAZING   AND    SOLDERING  171 

known.  The  whole  subject  comes  under  the  study  of  alloys,  in 
which  there  is  still  much  confusion  and  little  accurate  informa- 
tion. New  alloys  are  being  put  on  the  market  every  day,  some 
of  them  of  known  constitution,  some  unknown;  many  of  them 
have  properties  claimed  which  they  do  not  possess,  and  the 
practical  men  must  find  out  for  themselves  which  of  the  solder 
alloys  are  fit  for  the  purposes  they  are  advertised  for.  The 
future  will  see  more  accurate  information  at  the  call  of  the  metal 
worker,  who  will  be  able  to  choose  his  solder  with  an  eye  to  get- 
ting certain  properties  in  the  alloy  and  at  the  lowest  cost. 

The  soldering  bit  is  a  copper-headed  tool  used  to  melt  and 
manipulate  the  solder.  The  head  is  of  various  shapes,  accord- 
ing to  the  work  at  hand,  and  is 
fairly  bulky  so  that  it  will  hold 
heat  for  a  period  of  time  (see  Fig. 

\        TI    •       i  •         i  FIG.  qi. — Ordinary  soldering  iron. 

91).     It  is  also  pointed  so  as  to  be 

handy  for  working  into  seams  and  corners.  The  bit  should 
be  coated  around  the  point  with  tin  or  the  solder  that  is  to  be 
applied.  This  is  so  that  when  hot  it  will  be  coated  with  a  skin 
of  melted  metal  which  will  draw  the  solder  with  it.  To  tin  the 
bit  it  is  first  filed  or  sand-papered  free  of  scale,  is  fluxed  with 
zinc  chlorid,  and  then  heated.  It  is  then  tinned  by  holding  a 
tin  stick  against  it  and  melting  off  some  of  the  tin,  which  will 
adhere  to  the  freshly  fluxed  surface.  If  the  bit  is  at  any  time 
heated  to  redness  while  using,  the  tin  will  volatilize  and  the  bit 
must  be  retinned. 

An  ingenious  soldering  bit,  or  iron,  recently  patented,  is  de- 
scribed in  the  Brass  World  for  February,  1905.  The  body  of  the 
bit  contains  a  small  reservoir  in  which  is  placed  the  solder.  The 
reservoir  has  an  opening  near  the  head  of  the  bit,  which  is  opened 
by  pressing  a  lever  on  the  handle  of  the  bit.  The  reservoir  is  so 
designed  that  the  solder  will  not  .spill  out  while  the  workman 
is  using  it. 

Fluxes  for  ordinary  plumbing  soldering  are  sal  ammoniac, 
borax,  resin  in  alcohol,  tallow,  or  zinc  chlorid  solution.  There  are 
a  number  of  patent  or  secret  fluxes  on  the  market,  and  many 
metal  workers  make  their  own  special  preparations.  The  solder- 
ing flux  is  generally  applied  before  heating  and  after  the  metals 


172  WELDING 

have  been  cleaned.  Its  office  is  to  combine  chemically  with 
any  oxid  left  after  the  mechanical  cleaning  and  also  to  dissolve 
any  grease.  A  well-fluxed  surface  is  made  of  raw  metal,  ready 
to  be  wet  by  the  solder. 

Sal  ammoniac  may  be  powdered  on  or  applied  with  a  brush 
as  a  solution  in  water.  Calcined  borax  is  powdered  on  or  its 
solution  painted  on.  Zinc  chlorid  is  made  by  dissolving  zinc  to 
saturation  in  dilute  hydrochloric  acid.  It  is  considered  the  best 
flux  for  plumbing. 

Some  solders  are  known  as  self-fluxing.  They  contain  a 
metal  which  oxidizes  when  heated  or  which  is  a  solvent  for  the 
oxid  on  the  surface  to  be  soldered.  For  example,  Richards'  alum- 
inum solder  is  applied  without  flux.  It  contains  phosphorus, 
which  acts  as  a  flux  with  oxid  of  aluminum.  Self-fluxing  solders 
should  become  popular  in  the  future,  when  they  are  better 
known. 

Soldering  commonly  requires  much  less  heat  than  welding  or 
brazing.  The  solders  have  melting  points  one-half  to  one-fourth 

as  high,  and  the  joints  do  not  need 
to  be  annealed  or  cooled  slowly. 
Hence  a  mouth  blowpipe  with  a 

FIG.  02. — Ordinary  mouth  blowpipe.  ..       _  _,.  , 

candle  flame   (Fig.  92)  or  a  foot 

pump  with  a  gas  flame  will  give  all  the  heat  needed.  In  solder- 
ing large  joints,  where  the  heat  is  conducted  away  rapidly  by 
the  body  of  the  metal,  a  gasoline  or  kerosene  torch  is  used  for 
preheating,  and  the  solder  is  melted  in  a  tinner's  soldering  furnace. 
For  soldering  jewelry  and  filigree  an  ordinary  blowpipe  is  used. 
No  special  precaution  need  be  taken  with  the  flame,  except  to 
keep  it  hot  enough  to  consume  all  of  its  carbon.. 

I  will  not  try  to  describe  any  special  soldering  process.  There 
are  too  many  metals  that  can  be  soldered,  and  too  many  ways  to 
solder  them,  and  too  many  special  solders  for  a  given  joint.  In 
general,  the  process  of  soldering  includes:  the  mechanical  cleaning 
of  the  surfaces  of  the  metals  to  be  soldered;  the  heating  to  a  point 
where  the  solder  will  unite  with  the  clean  surfaces;  the  fluxing  of 
the  surfaces,  before  or  after  heating,  so  that  the  metal  surfaces 
will  be  really  clean;  the  application  of  the  solder  with  the  bit;  and 
the  finishing  of  the  joint. 


GRAZING   AND    SOLDERING 


173 


Blue  Cone 
(Oxydizing) 


Pale  Red  Flame 
(Reducing) 


In  cleaning  the  metals,  remove  the  rust  and  grease  with  a 
file,  scraper,  and  a  rag  or  alkali  solution.  If  the  flux  is  a  liquid,  it 
is  best  to  first  heat  the  metal  a  little  and  then  paint  on  the  liquid, 
which  will  eat  away  the  oxid  film,  and  will  keep  the  clean  surface 
covered  until  the  solder  is  applied.  If  the  flux  is  borax  or  resin 
in  solution,  first  apply  cold. 

The  solder  is  then  melted  on  to  the  hot  clean  metal  with  a 
torch,  or  by  pressing  the  hot  bit  against  the  solder  stick  and 
running  it  on  to  the  metal.  The 
bit  is  used  to  manipulate  the  solder 
over  the  surfaces  and  to  give  it  the 
proper  shape  as  it  cools. 

Among  the  precautions  neces- 
sary are  to  be  sure  the  metals  are 
clean  wherever  the  solder  is  intended 
to  bind.  This  can  only  be  done  by 
careful  fluxing.  Then  the  metals, 
must  be  hot  enough,  but  not  too 
hot.  If  too  hot,  they  will  be  liable 
to  oxidize  in  spite  of  the  flux,  should  the  flux  be  prepared  for  a 
low  temperature  only.  Also,  if  the  metals  are  too  hot,  they  will 
make  the  solder  highly  liquid.  The  bit  must  not  be  heated  too 
strongly  or  the  tinning  will  be  driven  off  and  the  bit  will  then 
be  no  more  capable  of  guiding  and  shaping  the  melted  solder 
than  would  a  stick  of  wood. 

Many  soldering  runs,  such  as  are  found  in  the  manufacture  of 
fruit  cans,  are  now  done  by  automatic  machinery;  the  cleaning, 
fluxing,  and  soldering  being  done  in  an  endless  chain,  and  the 
machine  turning  out  the  finished  soldered  job  in  a  tenth  the  time 
it  would  take  by  hand,  and  making  a  neater,  evener  job.  The 
soldering  is  done  by  dipping  the  fluxed  metal  in  a  bath  of  molten 
solder. 

The  following  solders  are  used  for  lead,  zinc,  copper,  brass, 
iron;  and  with  the  addition  of  cadmium  or  bismuth,  for  tin 
and  britannia. 


FIG.  93. — How  to  hold  the  blow- 
pipe in  a  candle  flame. 


WELDING 
Melting  Points  of  Lead-Tin  Solders1 


Name 

Lead 

Tin 

Melting  point 
deg.  Cent. 

Tin  

i 

i 

2->8 

Soft  solder. 

i 

2 

171 

Medium  

i 

I 

188 

Hard  solder  
Lead 

2 
I 

I 

227 

22O 

For  soldering  gold,  Gee2  gives  a  table  of  solders  with  melting 
points  of  983  deg.  to  1020  deg.  Cent,  composed  of  about  i  part 
copper  to  2  to  5  parts  silver,  and  a  small  addition  of  zinc.  In 
making  up  gold  solders,  it  is  quite  as  important  to  know  what 
metals  should  not  be  used.  Because  gold  is  very  easily  ruined  by 
certain  metals,  lead,  tin,  arsenic,  and  antimony  should  not  be 
used  in  solders.  Antimony  is  specially  injurious,  and  bismuth 
in  very  small  proportion  will  rob  gold  of  its  properties. 

For  silver  the  hardest  solder  is  4  parts  silver  to  i  part  cop- 
per. A  softer  solder  is  4  silver,  i  copper,  and  i  zinc.  About 
5  per  cent,  tin  makes  a  quick-running  solder.  Arsenic  in  vary- 
ing amount  is  also  added  to  soften  the  solder. 

For  platinum  the  solder  was  commonly  gold  of  ordinary 
purity,  melted  on  with  a  strong  blowpipe.  Since  the  introduction 
of  the  oxy-hydrogen  flame,  platinum  is  seldom  soldered  and 
almost  all  joints  are  welds. 

Aluminum  has  been  much  experimented  on  recently  (see 
page  21).  There  are  a  number  of  aluminum  solders  on  the 
market.  One  of  the  best  known,  Richard's  alloy,  is  composed 
of  22  tin,  ii  zinc,  i  aluminum,  i  phosphor-tin.  This  is  a 
self-fluxing  alloy,  due  to  the  action  of  phosphorus  on  the  alum- 
inum oxid.  Aluminum  solders  are  pronounced  in  general  to  be 
unsatisfactory,  because  aluminum  is  electropositive  to  all  other 
metals,  and  electrolytic  action  of  a  destructive  nature  is  apt  to 
set  in  some  time  after  the  joint  is  made,  especially  if  the  joint 
is  exposed  to  water.  Tin  is  harmful  to  aluminum  and  should 
not  be  used  in  its  solders.  It  is  claimed  that  tin  will  permeate 
into  the  aluminum  in  time  and  make  it  rotten  and  brittle. 

lBrass  World,  Nov.,  1905. 

2 "The  Goldsmith's  Handbook,"  Geo.  E.  Gee,  1903. 


GLOSSARY    OF    TERMS  175 

GLOSSARY  OF  TERMS 

Burnt  Metal. — If  iron  or  steel  is  heated  to  bright  white,  it  will 
crystallize  when  cooled.  This  will  make  it  brittle,  and  makes 
the  wrongly  called  burnt  iron.  To  prevent  this  brittleness  the 
metal  must  be  worked  or  hammered  when  cooling.  Steel  espe- 
cially is  easily  burnt  because  its  carbon  is  apt  to  crystallize  with 
the  iron  to  form  brittle  alloys,  above  bright  red  heat. 

Chamfer. — To  bevel  the  edge  of  a  sheet  or  bar  of  iron  so  that 
it  will  be  the  proper  shape  for  welding. 

Cold-short. — When  a  metal  is  brittle  below  incandescence. 
Generally  caused  by  an  impurity,  as  i  per  cent,  of  phosphorus 
in  iron.  Pure  zinc  is  cold-short  at  about  260  deg.  Cent.;  alumi- 
num above  600  deg.  Cent.  The  latter  may  be  said  to  be  hot- 
short,  but  not  red-short. 

Critical  Temperature. — Used  to  designate  the  temperature 
at  which  the  metal  itself  or  any  important  constituent  begins  to 
crystallize.  The  more  sharply  denned  are  the  critical  tempera- 
tures, the  less  weldable  is  the  metal,  as  high-carbon  steel. 

Ferrite. — The  mineralogical  name  for  pure  iron,  to  distin- 
guish from  martensite,  cementite,  etc.,  which  are  terms  for  the 
iron-carbon  series. 

Flux. — Any  substance,  compound,  or  mixture  used  to  clean 
the  surface  of  the  substances  to  be  welded  or  soldered.  The 
flux  must  be  chemically  or  physically  active  toward  the  surface 
impurities,  but  not  toward  the  substances  to  be  joined.  Sand  is 
a  flux  for  iron,  as  it  forms  a  fusible  silicate  with  the  iron  scale,  but 
has  no  affinity  for  the  iron.  Zinc  chlorid  is  a  flux  for  lead,  zinc, 
copper,  etc.,  to  be  soldered,  as  it  dissolves  the  surface  oxids, 
leaving  a  clean  surface. 

High-carbon  Steel. — A  general  term  for  a  hard,  brittle  steel. 
The  carbon  content  is  about  o.  50  per  cent,  or  more. 

Oxidizing  Flame. — A  flame  is  commonly  caused  by  the 
chemical  union  of  oxygen  with  another  substance.  If  the  flame 
has  more  oxygen  supplied  it  than  is  needed  for  perfect  combustion, 
the  free  oxygen  in  excess  makes  it  an  oxidizing  flame — one  that 
rusts  or  burns  the  metal.  A  flame  may  be  oxidizing  in  one 
place  and  reducing  in  another. 


176  WELDING 

Red-short. — When  a  metal  becomes  brittle  at  a  red  heat,  it  is 
said  to  be  red-short.  Generally  caused  by  an  impurity,  as  i  per 
cent,  of  sulphur  in  iron,  or  a  minute  quantity  of  bismuth  in  lead 
or  gold. 

Reducing  Flame. — A  flame  in  which  the  fuel  is  in  excess 
of  the  oxygen  necessary  for  perfect  combustion.  The  tendency 
of  such  a  flame  is  to  draw  some  oxygen  from  the  burned  parts  of 
the  metal.  At  all  events  it  prevents  burning  within  its  radius. 

Spelter. — Now  used  in  commerce  as  the  name  for  pure  zinc. 
Spelter  is  also  the  name  for  half-and-half  brass  used  for  brazing. 
The  best  way  to  use  this  term  is  not  to  use  it  at  all. 

Swage. — A  shaping  tool,  used  in  finishing  a  weld. 

Upset. — To  enlarge  the  metal  pieces  at  the  place  where  they 
are  to  be  welded.  The  enlargement  at  the  welded  joint  is  called 
the  upset. 


INDEX. 


Acetone,  94 

storage,  95 
Acetylene,  75,  90 

dissolved,  94 

flame,  96 

generator,  91 

storage  tanks,  96 

welding,  101 

vs.  riveting,  106 
Air  gas  torch  for  brazing,  167 

hydrogen  flame,  using,  119 
process,  118 
torch,  117 
Alloy,  aluminum,  21 

brazing,  166 

copper,  25 

gold,  1 8 

in  brazing  gold  and  silver,  169 

nickel,  27 

platinum,  17 

Richard's,  174 

silver,  19 

soldering,  170 

welding,  99 
Aluminothermics,  122 
Aluminum,  20 

in  welding  iron,  9,  1 1 

solders,  174 

welding,  23,  99 
Armature  shaft,  weld,  151 
Armor  plate,  annealing  with  Thomson 

welder,  70 
Arsenic  steel,  1 1 
Auto  frame,  welded,  109 

Bar,  for  top  welding,  2 

melt,  97,  98 

welding  to  plate,  60 
Bauschinger,  Prof.,  results  of  tests  by,  13 
Bernardos  arc-welder,  33,  35,  38 

process,  cutting  wrought-iron  plate,  42 

12  177 


"Betsy  Ann,"  repair  of,  147 
Bevels  for  strong  weld,  100 
Bit,  solder,  171 

Blow  holes  in  thermit  weld,  132 
Blowpipe,  holding  in  flame,  173 

hydrogen  air,  117 

mouth,  172 

oxy-hydrogen,  117 
Boiler  repairs,  102 

welded,  102 

Boracic  acid  as  flux,  165 
Borax  as  flux,  165 
Boxes,  mold,  for  thermit  work,  127 
Brass,  welding,  99 
Brazing,  165 

Ferrofix  process,  160 

practice,  167 

repeat,  169 

stock,  169 

Break-switch   Thomson,  49 
Bronze,  welding,  99 
Burner,  oxy-hydrogen,  118 
Burnt  iron,  143 

metal,  175 
Butt  weld,  4,  100 

welding  pipes,  129,  137,  140 

Can,  plunger,  142 

Carbid-feed  acetylene  generator,  91,  92, 

93 

Carbon  content  of  welding  iron,  9 
Cast  iron,  8 

iron,  welding,  97 

welding,  66 
Castings,  mending,  141 

repairing    with    oxy-acetylene    flame, 

1 08 
Chain  making,  2g 

welding,  30,  61 
Chamfering,  175 
Chemistry  of  oxy-acetylene  flame,  113 


i78 


INDEX. 


Chemistry  of  thermit  reaction,  152 

Chrome  steel,  n 

Clamps  for  welding  vertical  pipe,  139 

Cleaning  pieces  for  thermit  weld,  133 

Cleft  weld,  4,  5 

Coal  fire  for  welding,  2,  5 

Coke  fire  for  welding,  2,  4 

Cold-shortness,  175 

Colors  of  heated  metals,  i 

Contact,  imperfect,  6 

Cooling,  slow,  9 

Copper,  25 

in  welding  iron,  1 1 

power  and  time  required  to  weld,  58 

to  iron,  welding,  60 

welding,  25,  26,  56,  98 
"Corunna,"  repair  on,  148 
Costs,  cutting  steel,  112 

oxy-acetylene  welding,  112 

pipe  welding,  140 

thermit  rail  welding,  146 
Crank  case,  broken,  106 

case  with  welded  arms,  107 
Crucible  for  thermit-welding,  125 
Crystallization  point,  7 
Cylinder,  welded,  105 

Davis  acetylene  generator,  91,  92,  93 
Davis-Bournonville  Co.,  apparatus  for 

producing  oxygen,  86 
Detonating  gas,  80,  116 

Electric  resistance  heater,  69 

welding,  28,  33,  59,  70 
Electrolysis  of  water,  80 
Electrolytic  gases,  83 
Electrum,  19 

Energy  absorbed  in  electric  welding,  55 
Engine  bed,  welded,  108 
Epurite,  74 

Ferrite,  175 

Ferrofix  brazing  process,  160 
Fires,  welding,  4 
Flame-cutting,  in 

gas,  for  brazing,  166 

oxidizing,  175 

oxy-acetylene,  96,  101 
-hydrogen,  115,  116,  118 


Flame,  oxy -hydrogen,  reducing,  176 

welding,  5,  113 
Flue  welder,  64,  65 
Flux,  2,  3,  6,  175 
for  aluminum,  22 
brass,  99 
cast  iron,  98 
copper  welding,  26 
Ferrofix  brazing,  160 
soldering,  171 
in  brazing,  165 
plate  form,  158 
welding  gold  alloys,  18 
soldering,  165 
Touche*  torch,  75,  76,  78 
Furnace  for  brazing,  168 

Gas,  detonating,  80,  116 

flame  for  brazing,  166 
for  welding,  5 

welding,  101 
Generator,  acetylene,  91 

for  electric  welding,  44 
Girder  cut  by  oxy-acetylene  flame,  no 
Gold,  brazing,  169 

solders,  174 

welding,  18 
Graphite  in  welding  iron,  9 

Hadf eld's  steel,  10 
Hammering  in  welding,  4,  7 
Hazard-Flamand  cell,  82 
Heat  of  thermit  reaction,  154 

too  high,  7 

welding,  3 
Heating  metals,  57 
High-pressure  oxy-acetylene  torch,   77, 

78 

Hot-flame  welding,  73 
Hydrogen  air  blowpipe,  117 

Impurities,  effect,  8 
Iridio-platinum,  welding,  17 
Iron,  burnt,  143 

cast,  8 

welding,  97 

chain,  30 

for  welded  pipe,  29 

girder  cut  by  oxy-acetylene  flame,  no 


INDEX. 


179 


Iron,  malleable,  i 

power  and  time  required  to  weld,  57 

soldering,  171 

to  copper,  welding,  60 

weld,  i 

welding,  2,  56,  98 

wrought,  i,  7 

Joint,  brazed,  169 

plumber's  sleeve,  140 

thermit,  131 
Jump  weld,  4,  '6 

Kirkaldy  and  Son,  results  of  tests  by,  14 

La  Grange-Hoho  process,  electric  weld- 
ing* 33,  34 
Lafitte  joint,  6,  158 
welding  plate,  158 
Lap  weld,  4,  6 

welding  lead  sheets  with  air-hydrogen 

flame,  119 

Lead-tin  solders,  melting-points,  174 
Linde  process  of  making  oxygen,  83 
Lining  for  thermit  crucible,  127 
Liquid-air  process  of  making  oxygen, 

83 

Locomotive  flue  welder,  64,  65 
frame,  thermit  welding,  145 
Low-pressure   torch   for  oxy-acetylene, 

77,  78,  79 

Manganese  in  welding  iron,  10 
Melt  bar,  97,  98 

welds,  101 

Melting-point  of  lead-tin  solders,  174 
Metal,  burnt,  175 

cutting  with  electric  arc,  41 
with  oxy-acetylene  flame,  109 

heating,  57 
Mold  boxes  for  thermit  work,  127 

for  pipe  welding  with  thermit,  138 
thermit  work,  130 
welding  vertical  pipe,  139 

rail,  128 

safeguarding  in  thermit  welding,  134 

sand  for  thermit  work,  128 

thermit,  129 
Motor  armature  shaft,  weld,  151 


Nickel,  27 

plate,  27 

steel,  n,  27 

thermit,  136,  154 
Nitrogen  in  welding  iron,  1 2 

Oil  flame  for  welding,  5 
Osmium,  welding,  17 
Overheating  iron  and  steel,  3 
Oxone,  87 
furnace,  90 
oxygen  generator,  89 
Oxy-acetylene  blowpipe  weld,  140 
-acetylene  flame,  16,  101,  109,  114 
process,  73 

system,  high-pressure,  100 
torch,  41 

welding,  cost,  112 
-hydrogen  blast,  16 
blowpipe,  117 
burner,  118 
flame,  116,  118,  119 
process,  115 

Oxygen  apparatus  using  oxygenite,  86 
burner,  89 

constant  pressure  regulator,  81 
from  chlorate,  86 
generating,  74 
generator,  88 
in  cylinders,  84 
processes  of  making,  83 
storage,  83 
Oxygenite,  74,  85 

Phosphorus  in  welding  iron,  10 
Pipe,  butt  welding,  129,  137,  140 

welding,  29,  138,  147 
Piping  of  steel  ingots,  preventing,  143 
Plate,  welding  to  bar,  60 
Platinum,  15 

solder,  174 

welding,  17 

Plumber's  sleeve  joint,  140 
Plunger  can,  thermit,  142 
Poling,  143 
Potassium  chlorate  method  of  generating 

oxygen,  74 
Power  required  to  weld  copper,  58 

required  to  weld  iron,  57 


i8o 


INDEX. 


Preheating,  5,  97,  98,  99,  133 
Puddling  process,  i 

Rail,  electrically  welded,  67 

molds,  128 

patterns,  127 

thermit-welded,  67 

welding,  66,  68,  123 
Reaction  in  thermit  welding,  135 
Red-shortness,  10,  176 
Regulator,  oxygen  constant  pressure,  81 
Repair,  boiler,  102 

welding,  102 

with  oxy-acetylene  torch,  103 

work,  thermit,  130 
Repeat  brazing,  169 

welding,  43 
Richard's  alloy,  174 
Riveting  vs.  acetylene  welding,  106 
Roessler    and    Hasslacher   Co.,    oxone 

oxygen  generator,  89 
Royal  Prussian  Testing  Institute,  weld- 
ing tests,  13 

Sand,  mold,  for  thermit  work,  1 28 
Scarf,  2 

weld,  4 
Schuckert  apparatus  for  electrolysis  of 

water,  82 

Seal,  safety  water,  80 
Separation   planes   in    thermit    weld, 

132 

Setting  pieces  for  thermit  weld,  132 
Silicon  in  welding  iron,  9 
Silver,  19 

brazing,  169 

solders,  174 
Smith  welding,  2,  26,  31,  159 

welds,  tests,  12 
Solder,  170,  173 

for  aluminum,  21 
silver,  20 

hard,  19,  170 

self -fluxing,  172 

soft,  19 
Soldering,  165,  170 

bit,  171 

fluxes,  165 

process,  172 


Spelter,  176 

for  brazing,  166 
Sponge  platinum,  16 
Steel,  arsenic,  n 

chrome,  n 

compared  with  wrought  iron,  2 

cost  of  cutting,  112 

high-carbon,  175 

nickel,  n 

silicon,  welding  properties,  10 

thermit,  121,  152 

welding,  7,  98 
Stock  brazing,  169 

welding,  28,  30 
Storage,  acetone,  95 

oxygen,  83 

tanks,  acetylene,  96 
Sulphur  in  welding  iron,  10 
Swage,  176 

Tank,  welded,  103,  104 
Tap  hole  of  thermit  crucible,  126 
Tapping  crucible,  130 
Temperature,  critical,  7,  175 

of  oxy-acetylene  flame,  114 

range  of  weld  iron,  i 
Tests  of  acetylene  welds,  115 

of  electric  welds,  70 
Lafitte  welds,  159 
pieces  treated  with  Ferrofix,  163 
smith  welds,  12 
thermit  welds,  155 

welding,  13 
Thermics  of  oxy-acetylene  flame,  113 

of  thermit  reaction,  152 
Thermit,  8,  28,  147 

amount  to  use,  124,  131,  135 

commercial,  152 

crucible,  126 

in  foundry  practice,  142 

joint,  131 

mold,  129 

nickel,  136,  154 

plunger  can,  142 

poling,  144 

process,  108,  121,  144 

repair  work,  130 

titanium,  137 

to  prevent  piping  of  steel  ingots,  143 


INDEX. 


181 


Thermit,  welded  rail,  67 

welding,  practice,  131 

welds,  tests,  155 
Thimble,  126 
Thomson  automatic  break  switches,  49 

electric  welder,  45,  46,  54 

machine     for     welding     hubs     and 
spokes,  51 

process,  electric  welding,  33,  42,  66,  68 

reactive  coil,  48 

specimens,  61,  63,  64 

welders,  47,  50,  52,  53,  70 
Time  required  to  weld  copper,  58 

required  to  weld  iron,  57 
Tinning  soldering  bit,  171 
Titanium  thermit,  137 
Top  welding,  2,  6 
Torch,  air-hydrogen,  117 

for  brazing  or  soldering,  166 

oxy-acetylene,  75 
Tubes,  welded,  103 

Unwin,  W.  C.,  results  of  tests  by,  14 
Upsetting,  4,  176 


Water,  electrolysis,  80 

-feed  acetylene  generator,  92,  93 

-pail  forge,  34 

seal,  safety,  80 
VVatertown    Arsenal,    tests    of    electric 

welds,  70 
Weld,  different  kinds,  4,  6 

large,  8 

melt,  101 

poor,  causes,  6 

smithed,  2,  6,  12 

thermit,  146 
Welding,  electric,  28,  33,  59,  70 

hot- flame,  73 

smith,  2,  26,  31,  159 

with  gas  and  acetylene,  comparison, 

101 

oxy-acetylene  flame,  97 
Weldite,  154 
Working,  4,  7 
Wrought  iron  pipes,  29 

iron,  welding,  98 

Zerener  electric  blowpipe,  33,  34,  35 


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